Which does your friend speak when he speaks English? If his pronunciation, spelling and grammar are based on AmE, then that's what he should help his child with. Even if the child goes to classes, he/she will learn much more if someone at home speaks in English as often as possible.
If the child goes to BrE classes, but hears AmE at home, there are two possible outcomes:
1 - The child will get rather confused
2 - The child will end up speaking both versions very well.
There is no way to tell what will happen. However, if your friend doesn't speak English at all, then it's entirely personal choice which one he wishes to educate his child in.