S - Radios, get a programmable one that supports multiple models like the Spektrum 7. You'll pay more now but <$99 for each additional model. I have Four radios for four models (long story) and would rather lug only one around. Also I would highly recommend RealFlight G3 RC flight sim for you and your son to practice on this winter. I soloed with an instructor after three flights all because of the sim. It'll save you LOTS of money in model repairs. It is absolutley realistic (physics based software). It's one of the best all around computer games on the market too, tons-o-fun. Especially when you have friends over and let them give it a try. Everyone I've recommended this route to said it was the first investment they would've made getting into RC.

Don't forget to shop EBay.