Yeah i shoot my dads 12 gauge, but i cant handle the slugs
Which is perfectly reasonable. I was only able a couple years ago myself to become fully comfortable with the use of a 12 guage. Now I can use it consistently with no problem.
Eh, he has a point. If someone isn't trained properly they can (and, more than likely, will) seriously injure someone.
Which goes for anyone. If a kid that age is well trained and able to use it correctly with advlt supervision, then there is no reason not to.
Many advlts would be much more dangerous and inexperienced.