I would like to offer another suggestion...

As a fellow Minnesotan, I know that you will soon be experiencing the yearly devastation that we so loosly call "Winter". This is going to give you both lots of time when you can't fly - but you can still enjoy the thrills of "Dreaming of Flight" by building a kit.

Before you cast this idea aside, let me point out some advantages.

In the long run, it's going to cost about the same as an ARF or RTF, BUT, you don't need to spend it all at once. Get him a kit for Christmas (Birthday, Chanuka, Kwansa, Etc.) You can now pick one or two nights each week when you will be building together (you'd be surprised at how interesting it can be for BOTH of you). Granted, you'll end up doing most of the thankless parts, but you will also be gaining a wealth of knowlege which will come in handy for doing repairs.

As (quality) time goes by, you can aquire an engine, radio, and whatever else you will need. Meanwhile you can be attending meetings of your local club (I know there are several good ones in your area), and start to get to know the guys. Eventually, you'll find one that you will want to train with (Instruction is free, basically you just want to find someone who you think knows his stuff, and you'll enjoy spending the time with). This person can also give you advise on what type of radio to get (They are all good, but it's good to get a brand that is compatable with your instructor's so that you can connect the two for training purposes.)

The guys in the club will also offer to assist in any building problems you might encounter, and often loan you special tools for making some jobs easier. They will also give your plane a good going ove throughout the building process to make sure that you haven't made any bone-head mistakes (we've all done it!)

Before you know it, Spring will be here and you'll be ready to take your pride and joy out to the field with the confidence that you now have a better understanding of what you are doing, plus you have spend an otherwise dull, boring winter spending quality time with your son, while both of you enjoy the dream of flying while your project is coming together.

PS, Many kits nowadays are very easy to assemble with step by step instruction, and excellent fitting parts.