Now that I'm a self-styled family biking <airquotes> expert </airquotes>, I do get asked a bit about what bike or seat is best for such and such family configuration. And I'm always happy to answer at greater length than is perhaps hoped for.
So here it is, my opinionated take on what bike setup you need for you and yours. I should note my biases: for cycling a la familia I like big bikes (and I cannot lie). Big sturdy practical bikes with cargo capacity. Because you'll soon want to do a lot more than drive your bikes to Sunday toodles along the bike trail, and having some ever-ready cargo ability makes bikes so much more practical for errands, school dropoffs, and everyday cycling ...
I also don't love bike trailers, which seem to be the default way to bike with young kids in this country. Yes, they're easy to find, let you ride your existing road or mountain bike without much modification, work well with narcoleptic toddlers, and have good weather protection. BUT - the awkward maneuvering, lack of interaction with your kids, and the intense dislike or, at best, tolerance that they inspire in passengers (my daughter won't ride in a trailer unless another kid is along, which works until the squabbles start) make me unenthusiastic about trailers. In some respects, they might be safer than some of the other options below, but they can and do tip over.
If you like to ride bikes for the wind on your face, swoopy turns, the sensation of self-powered speed, and getting to experience the world around you with all of your senses ... then so will your kids! if you're a reasonably confident & careful rider, don't miss the delightful conversations and shared delight that comes with riding together on a family bike. Get giddy.
So find your current and future family configuration below, and see what might work for you. I'm sure other family cyclists will have their own opinions (here's another family biking overview, and another, and another). Please comment below about what's worked for you, and I'll keep this page updated with evolving options and opinions. This is a work in progress ...
Photo Credits: All photos are linked to original flickr post. Apologies for not including credit captions - I lack the web-fu to do them on side-by-side images here.
Car seat in bakfiets > MADSEN with custom insert > adapted bike trailer
This baby on bicycle section got so convoluted that it became its own blog post (you know you want to do it ... click the link). A bakfiets "box bike" takes the cake for this age, and grows nicely with your family. But we like our DIY infant seat in the MADSEN too.
Front seat > MADSEN or bakfiets or xtracycle with seat > trailer
If you have a toddler, and want to go by bike, don't miss out on your chance to ride with a front child seat (see link for big front seat rundown and safety tips). As another biking dad put it, it's a 10MPH hug. Having your young child in between your arms as you ride along, pointing out trucks and geese and planes, waving to folks as you pass, and frequently squealing with glee is amazing - truly one of my favorite parenting experiences so far. Your toddler will feel that they're driving "their bike", and will be considerably more enthused about riding with you than when they're slumped in a trailer with their helmet tipped over their eyes.
MADSEN "precious cargo bikes" and bakfietsen (or similar, like the Metrofiets above) work well too, and add room for friends and groceries. And an Xtracycle "sport utility bike" with a Bobike Maxi/Peapod rear seat or custom seat is also a great way to go. But I prefer a front seat position for as long as the child will fit up there. The advantage that a bakfiets, MADSEN, or trailer have over a front seat is naps, which can be awkward or less safe in a front seat without a "napping pad" in front of the child.
Xtracycle or MADSEN or bakfiets > city bike with rear seat > trailerbike
A child this age will be too big for most front seats, so unless you've got a bakfiets, the kid moves to the back, where they get to enjoy the view of your hiney. With rear-loading seats (I like Bobike Maxi's) and bigger children, having a sturdy bike with centerstand or double-kickstand is important for loading safety and convenience. The first three up there have more stable stands and more cargo capacity than most city bikes, excepting the Dutch-style bikes with burly double kickstands. Older kids in this range might be ready for a trail-a-bike or other towing option, or could ride on an xtracycle with "stoker bars" (handlebars for them). They do need to stay awake for that kind of riding, however, and have some modicum of impulse control.
Bakfiets or modified MADSEN > front seat plus modified trailer
Bakfiets wins this one too, but we'll see how my MADSEN baby seat works out. I'd still prefer to have them where I can see them ... for now toddler Drew rides in a front seat and baby Luc's in the trailer.
MADSEN or xtracycle or bakfiets or "mamafiets" > trailer
This is a fun family biking situation, so look for a "party on a bike" option like the first ones up there. The MADSEN allows up to 4 kids to face each other, and in a bakfiets they can ride abreast, but an xtracycle one behind another solution is still plenty fun and is perhaps an overall more versatile bike.
A "moederfiets", or "mamachari" is a city bike with both front and rear seats. They come ready to roll like this in the Netherlands and Japan, but you can make your own with an "omafiets" (Dutch bike with step-through frame) or low-stepover xtracycle and 2 seats. A bike like this has an advantage if you want your kids separated for a more peaceful ride, or want a "normal bike" (if you're Dutch, that is) that happens to carry 2 kids.
Bike trailers work for 2 kids as well, but it's a little harder to intervene in the inevitable squabbles, which you may not hear until they get apocalyptic. Heck, in a MADSEN, you can even reach back and flail your arm around the backseat like your Dad used to do on road trips ... "He keeps thumping my helmet!" ... "I will pull the bike over this instant!"
FollowMe Tandem / Trail-Gator or xtracycle with bike hauler or Family Tandem or trailerbike
If you have a child that's riding their own bike but isn't yet ready to negotiate traffic, a FollowMe Tandem or Trail-Gator is really handy for school drop-offs and the like, as it allows a parent to tow their child on busier streets, but also easily detach the child's bike for independent riding. And there are several ways to carry or tow another bike with an xtracycle, either using a rack on the side-loaders, or attaching an axle clamp at the rear and towing, which is another nice way to carry child and bike. But the first options allow the child to pedal with you, which is sometimes preferable.
If you're able to trade up to yet another family bike, there are a number of family tandems out there like the KidzTandem, where the child rides in front, or modified traditional tandems where the child is the stoker in the rear. I hear lovely things from families that ride with setups like these. A trailercycle add-on (trail-a-bike, etc) is a easy, modular way to make a family "tandem" as well. It introduces some handling squirreliness relative to a real tandem, but cheap is good these days, and being able to remove it when not needed is handy.
Xtracycle or Family Tandems/Triples
An xtracycle seems ideal for occasional kid passengers, since it performs well as a solo bike for commuting and other practical purposes as your kids graduate to their own bikes, but is always ready to give someone else and their gear (or bike, even) a ride. For regular riding together, a family tandem or triple (or quad!) is expensive but a hoot. And instead of towing kids, you get extra kid pedal power!*
* Kid power variable and intermittent, with bursts of herky-jerky, your mileage may vary.
Family Tandems/Triples Plus Trailers or Longbikes
Wherein I finally endorse a bike trailer ... for maximum clown car effect on the back of an absurdly long bike. And if you've got nice quads (multiples, not muscles), MADSEN has you covered.
Runbikes or pedals-off bikes -> Practical & stylish kids' bikes
The current state of kids' bikes in this country leaves a lot to be desired, but we're optimistic that more sensible options will be available by the time our toddler hits this stage. Until then, here's a nice series on making the bike above right, and a discussion on BikePortland.org.
Still confused about what to get? There are a lot of specialized options up there, so let's just keep it simple.
Best All-Rounder Family/Cargo Bike: Xtracycle. Versatile, nimble, and homegrown on our West Coast, with a great community of family riders and official/unoffical add-ons.
Up-and-coming: MADSEN's are close behind, though, as they're ready for young kid transport without expensive or custom seats. They're actively working on a lot of the 1st gen issues, and have a cabriolet-style raincover and electric assist in the works.
Just One Kid: Go Dutch, unless you have hills, in which case a lighter city bike would be better. A burly city bike will get you and your kid and your cargo around with aplomb. Carry your sweetie on the back rack while you're at it.
Best Bike for Young Families: A tie between MADSEN and bakfiets. Depends on your budget and your hill situation.
Cheapest Way to Go: Have you noticed that I like shiny pricey Euro-bikes? You could also just go with an Ebay child seat or Craigslist bike trailer on a used steel-frame bike with potential, or your old MTB in the garage. But start saving ... you'll want to city bike it or xtracycle it before long.
Best Kid Seats: Bobike (Mini in the front and Maxi or Jr. in the back). UPDATE: Yepp seats have pretty much swept the market in the past 2 years, and yes, they're great.
Best Family Bike Shop (and blog): Clever Cycles, in Portland, OR. I do love my local Dutch Bike Seattle and Aaron's Bike Repair (both of whom have excellent websites too), but the Clever crew have more family bike options, oodles of family & carfree expertise, dynomite customer service, a gorgeous store that's like Willy Wonka's for bikey people, and a blog worth reading from start to finish.
Most Inspiring: Xtracycle. The folks that started the longtail trend have a lovely company personality, what with their website & tweets, their bike activism, their generous attitude to newer competition, their slogans ("Every day adventure", "Where practical meets magical", etc ...), and their slideshows. I'll leave you with this one: