You want a high level compiled language to learn programming theory.
C# XNA Java , C++, even Delphi.
There's bucket loads to games programming. The trick will be to get him programming and enjoying that. That will carry him into games. Not matter how intelligent and well educated the wee fella is, starting up with tic tac toe or noughts and crosses is going to stretch him for a first go.
Animations is always a good start, then sprites (moving animations)
One of the first successful games I ever wrote was eight different coloured squares moving at random speeds, from one side of the screen to the other. Make sure him and his mates don't start betting on them though :D
Set his expectations, even with modern tools, modern games are an enormous effort. So if he's basing his interest on what he's playing, he'll be very disappointed.
I'd have to spend weeks doing something like the old atari tennis game. Tetris or break out would be a challenge. State of the art stuff, I wouldn't even know where to start without educating myself a lot.
Is he good at and interested in maths, he'll need it.