Oh boy! I hope you're going to let him shoot reactive targets. My kids loved to watch cans full of water or soda cans explode when a 22 hit. The big favorites were soda cans, clay pigeons and a steel target that spun when hit.
Then there was the prairie dog trip. My son still talks about some of the hits he had with those exploding 'dogs. I guess not all kids would like that, but my boy did.