Check his lower a-arms. If the ball-joints are not removeable I don't think he can powdercoat them. The uppers will be OK though.

 

If he can't have it powder coated what is a good paint use?

 

Your son and I are in the same boat! I just had my 250R frame powdercoated but not the a-arms. On my arms I am using Premium Decor exterior high heat spray paint. It will withstand heat and I'm told it is very tough. Tell him to put a-arm guards on like I am doing that way he'll have extra protection so the paint wont get scratched.