Well I would definately start him off on a 22lr in a bolt action or lever action. Something that he cannot get into the bad habit of just squeezing the trigger over and over again until he hits his target. Get him used to taking his time to aim, breath and squeeze the trigger. One other reason to use the 22lr over the .17 is because they are cheap to shoot and he can get lots of practice in. Then when it is time to start hunting big game, how could you go wrong with a lever action 30-30? Easy to handle, light recoil and short enough for shorter arms. If you need to go with a lenger range bullet then a .243 would be the next best option. Low recoil and a wide range of rifle styles to fit him. My son is 13 and took his first deer this year with my .270, which he likes to shoot. So that may be another option. The nice thing about a .270 is that it has the capability to take larger game as well as deer, coyotes, etc. Have fun and good luck on making some good memories with your son.