I have been teaching Hunter Education and 4H Shooting Sports for many years. Success breeds interest while failure breeds discontent. Hitting with a rifle will encourage him, while missing with a handgun will discourage him. I suggest buying him a nice light caliber rifle, e.g. .243 with a good scope. If you have a rimfire handgun, allow him to shoot it. Let him progress at his own pace as this is an important juncture.