This is the reverse of a speed race. Plan a course the length of the area; with chalk, draw lanes about 3' wide.
Several boys compete at the same time. They must ride as slowly as possible, without touching a foot to the ground or crossing the chalk lines, or stopping. The winner is the last to reach the finish line. If a boy commits any of the fouls described, he is eliminated from the race. If nobody can reach the finish line, the one who travels the greatest distance is declared the winner.