Rummer nailed it on this one.......I got my first BB gun at 7, shot gun at 10, and 22 at 11. I was allowed to shoot the BB gun anytime, but wasn't "turned loose" with the shotgun or rifle till I was 13 or so.....
Just like Rummer, I was taught safe gun handling in the den, long before handling around other people.
I think it wise to start a bit earlier now, before public education teaches the kids that guns are bad, animals have rights, and the other liberal spin that "educated people" like to propagate.