Fast gratification is the key with youngsters. He probably doesn't care about perfectly round loops and greaser landings like you do. He just wants to fly. To that end, the sim is a good idea for the winter because it's fun, but when it's time to get a plane I'd go the foamy route. They fly well enough in low wind to be fun, and they are easy to fix. Let him enjoy those and if he sticks with it for more than a month maybe let an instructor take him up on your trainer.