Good deal for him! If he can have the patience to follow the steps in the training manual or as noted above Ratz method - parking lot, Eagle, Flinstone, relax, straight lines, gentle pedals, relax, relax, figure eights return many times for short training is more effective than one long session -Then he will be faster than you in a momentarily, and more comfortable.
Lucky sot! - err son! I got one new bike before I was 20 and that was a wedgie mountain bike from my grandpa around grade 5 - man I loved that bike. Think my parents still have it for visiting chillins, Norco Mini-Mountaineer. Thanks for triggering the good memories.