http://www.garagegames.com/ is a great engine to work with for games. It starts you off with basic games that can be extended and has an active community. It is c++ so its a little harder but also has a very nice scripting component that he could program in to start with. The engine is often used in a "GameInADay" event where people program entire games with it in 24 hours. Granted they arn't spectacular games but that gives you an idea how solid a foundation it will let you start with.