Excellent visual Pete.
Correct, the only laws for kids to ride quads are ability to reach and operate all controls and be directly supervised by an adult (Kid or Adult must have taken the AT Safety course).
As long as the kid can reach the foot pegs and hand controls with ease...no issues. The ATV Safety Cert, they don't check for often unless they see your kid zipping round and no parent in sight, that's when they will roll up and start giving tickets. Watching your kid ride around camp from inside the trailer or motorhome doesn't count...LOL