As a NRA Instructor....I would never allow an 8 year old to fire a fully auto weapon without my hands on the weapon at the same time......
Geez....has common sense take a vacation???
Old Jarhead and lifelong shooter here- the exact same thing leapt into my head. If a youngster wants to take a crack at it- first make sure it isn't something that's going to overwhelm him/her, then keep your hands on it all throughout until the chamber is verified empty and magazine removed!