he sounds like he is gona be the next big Mat Hoffman  can't wait to see him on TV lol

Buy him all the protective gear you can find for his age, because if he has a talent he should go on, but he doesn't need to feel pain because he will asociate BMX and maybe a dream with pain. BMX is pain but at his age he might think that it is only pain and wont find any satisfaction in it. Watch out he may get bored and then all your work will finish with no result, but I think that if he starts BMXing at his age, well he might end up doing front-flips- back flips and tailwhips when he will be 11 or 10 years old. Support that kid he has potential, big one, not every kid could ride bikes since 2 years old and like bmx since 3 I got my first bmx when I was 10 so he should be a semi-pro by that age. Wish him luck. 10+++