Since no one else has commented I thought I would add that my son enjoyed Python but has not spent too much time trying to make games but used it to solve problems. He has been involved in the USACO competitions and this year we found that UCF has one online competition that he did.
I tried to encourage him to learn Java and had him do a week summer camp on it but he much preferred Python after the camp. He is taking AP Computer Science this year so finally he it has become necessary to learn Java and he has done very well (but still likes Python much better than Java).
I think I have seen that your son likes math so he might enjoy trying to write some programs to solve problems on Project Euler.
Good luck!
