We use either a trail gator or our Xtracycle to transport kids plus bikes. On the xtra we can take two kids plus two kid bikes and the kids can sleep, so that system usually wins. The kids ride specialized hotrocks, because they are relatively light and have good resale value. Our 5 year old rode a 23 mile day on his earlier this summer! But we would never have tried something like that, if we didn't have a reliable method for towing his bike while also carrying him.