To start with the AMA now has 0 dollars for membership if under 19 and living at home. So for him to join is now no big deal. Also being 16 his father is libel for any damages not him. The AMA would be secondary to his dads insurance, but without it his dad will carry the whole bill. Also some parks won't even let electric to fly. You must find out. Also a lot of clubs have JR membership dues, that maybe less.
It's great you had no problems and I hope in the future you continue to enjoy the hobby. Dennis