OK, I believe that if we left our cars at home, we collectively would be a healthier, greener nation, but the main reason I’m sharing this list of frickin’ sweet bikes is that they look like sooo much fun. Don’t worry about the kids keeping up or how they’ll deal with traffic: co-ride on these bicycles built for two (or more).
For two:
First came the SUV, then the SUB, as in sport utility bike. The Kona Ute Cargo Bike (above, $899) is longer than an average bike so it can haul big, heavy loads behind the rider. With room for grocery bags and a passenger, the Ute can be a green alternative for short adventures or errands. The passenger — adult or kid — does have to be able to balance, so you’ll have to use your wise parental judgement about when your kids are ready. With that in mind, handy folks have found ways to add a secondary set of handlebars and pegs for the passenger’s feet.

Think of the Love Bike ($890) as a compact tandem bike. The child can ride up front for a better view — you know, besides your bum. For little kids, stationary pegs are available as foot rests, or bigger kids can pedal along with the parent. It’s rare to come across a vehicle that puts the controls in the back seat, but the Love Bike does. Parents steer, shift and brake — or could ride the bike solo.

Brown Cycles KidzTandem ($1,949) looks like a regular tandem bike except that the front can accommodate 4-7 year olds or 1-4 year olds with the company’s Quick-change seat. Again, kids get the non-bum view while the parent controls the when, where and how of the ride. If you’re searching for something more aggressive, Brown Cycles also makes a road version, $2,399.
For three:

Whether you’re trying to fit the parents and a kid or one parents and two kids, the Co-Motion Cycles PeriScope Trident ($5,795) seats three. The Trident’s seat adjust to fit most riders, and like with most tandems, the first rider handles the controls. Keep in mind riding tandem requires some additional skills that a single bike does not require, like teamwork when stopping and starting (and staying up).
For more:
It’s probably safe to say you can ditch any gym memberships if you’re the human motor of the Sorte Jernherst Coach Trike ($5,549). This trike leads with two wheels that support the, for lack of a better term, kid box. The box seat six kids (yes, six!) on two foldable bench seats that have six hip belts. Should the weather turn nasty, the box also has a “sunbrella” that covers the passengers but not the driver. Supposedly, they’re common in Europe, but I gotta say I haven’t seen one in real life in the U.S.— but I'd like to!