When I bought my 45-70 the guy I bought it from threw in a box of the 300 grn hollow point Winchester ammo and half a box of Remington and it was the first ammo I shot because I couldn't wait to shoot it. After I got the lever evolution ammo it printed the same as the Winchester as well. So long as kids that age see interesting things they will sit, they get bored easily at that young age, the older he gets the longer his attention span will be. You are doing it right. When he is ready to quit, you quit instead of making him sit there bored. That is a good way to get the opposite result you are trying to foster.