I don't think there is a certain age requirement with credit cards because you can always get an account merged with your parents, so you have a tap on your parent's money if you "have to use it" is .. well, what the parents say.
I'm guessing this is why he has a credit card rather than a debit card, because a debit card, you spend your money, it's gone, you'll never see it again.
Now, clipto, as said by many so far, contact the developers (
www.liveforspeed.net and click on contact us), otherwise I might have to lock this thread soon before it gets out of hand.