Well, as far as I know, the ATF check needs you to be over 18. Now I'm not sure if Disney has a different age requirement since I was well over 21 when I was there. The only cast members who can give him a true explanation is someone who actually HAS a pyro card. If they don't, then they don't know what they are talking about. Even if he isn't "of age" yet, you don't need a pyro card until you hit the point where you are physically handling product (pyro) yourself. If you are just on shows with pyro, you don't need it, so if he's just a hair under, they could still use him and just not do his certification until he turns 21 (if that's the case). I didn't get pyro training till several weeks into my position and they pushed me through a bit quicker because I came in with 10 years of pyro experience to start with and they were putting me on the fast track to get on the Wishes crew. I would tell him to at least learn a few things about pyro. Can't remember what all they asked in the interview, I know one of the questions was pyro grades, so here's a tip - 1.4G - Consumer or "stage" pyro - stuff that can be fired close to performers or crowds, 1.3G - professional grade "big stuff" - mainly shells that go in the air. That's the stuff people are used to see during a "fireworks show", 1.2G - demolition grade, 1.1G - military grade - basically the smaller the number, the more heavy duty the explosive.
