My eight year old son loves guns. And cars. He's either going to be a Cavalry Scout or a getaway driver.
He likes driving go-carts, and he can, with me in the passenger seat. He likes shooting his Remington 714, and he does, with me alongside him.
He doesn't drive my car, though, and he won't shoot full auto for quite awhile, because neither activity is safe for him.
Leave the full-auto for full-size people.