SKnot had a bike at 2. He really liked it. (it was when we took the training wheels off another bike years later that the biking thing fell apart) The seat was low enough that he could touch the ground and he mostly pushed himself with his feet. Pedalling came later. (before the bike he had a plastic trike without pedals, so he had the foot-push down)

Can Xander have the goal of just making the thing move, instead of trying to get a certain distance? Or is it his idea to go to the mailbox?