I took the game for a spin and enjoyed it!
I'm a lead developer of HTML5 educational games for sites like mathsnacks.com, so of course I really liked seeing a cool math game that's fun to play!
Looks to me like your son's got the aptitude, interest, and skill to be a game developer. I hope he pursues it and enjoys making more games!
Our studio runs a blog about educational games, including math games. Would you mind if we write a blog post about the game and link to it?