Another option to look at is a Bike Friday tandem or triple. I just looked on their web site, and here's part of the description for one of their tandems: "The Family Tandem is fun for the whole family! It easily adjust to riders from 4'10" to 6'5" (front) and 36" (w/ the optional child adapter) to 6'2" (rear). "

They also make bikes (their Q models) that convert from a tandem to a single or from a triple to a tandem.

--- Denise