We put a carseat in our bike trailer when the kids were infants and transported them that way most of the time. I once went to a WATS meeting in winter like this with our daughter. We eventually had to buy a bigger trailer to carry both of them. We bought a Wike trailer, which had far less cargo capacity, but was excellent for carrying around two kids. It folds and converts to a stroller and folds down completely for storage as well. (I miss our Wike, and having two kids small enough to use it.)
Contributed by: Ken Clark
Also, from Karen Smith's recent comment:
Man! Why didn't I do this sooner? I just bought a kid trailer for my bike. It's great! (Chariot Cougar double). Now I can take both the twins to around town by bike---before we always had both parents hauling each one kid to get around (or one parent went by bus). So now hubby can snooze on the couch while we go to more exotic parks (or vice versa)! I should have done this 2 years ago.
The chariot cougar was a bit pricey ($435), but I think you get what you pay for in this type of purchase. We got ours at AA Cyclery on Packard (great store BTW).