Stumbling back onto topic for a moment, I've taken my kids (presently 6 and 4) pretty much everywhere on recumbents since they were about 18 mths old. The most successful solutions were the trailer (lots of room for stuff you'd bung in a buggy, nice wide passes from cars) and the tandem (neither kid can reach the pedals, but they enjoy the ride). As above, the childseat solution is tricky as the COG is so high compared to the rider. That said, Ted has been known to do laps of the cul-de-sac perched on my rear rack without any issue.