Just for having fun and experiencing the thrill of flight, I would suggest a small electric plane for him. I've flow a few myself, and and now piecing one together for my 8 year old nephew. All I have left to get for it is a motor now. Thanks to Spaceclam for the ESC! I'm sure you could locate one around somewhere, once you learn to fly, they pretty much become boring to most. It's the electronics and such that are hard to come by as spares, they're reusable later, and move on to bigger and better things with the pilots!

Just my 2 cents.
Keith