What's your idea of the absolute minimum age you would let a young boy participate in model rocketry with adult oversight, obviously?

I’ve been toying with this idea for Christmas. He loves planes, equipment, noisy stuff, etc, and I’m sure he’d love this stuff. But the adult supervision in his direct family is lacking, if you understand my concern. And these things can be nasty if misused. I think I know my decision, but I was just interested in some other thoughts.