First off I think neither of you have any experience to just fiddle around with a plane. My advice is to go to a local club and start asking for help. In the long run you will be much more proficient at helping your son and have more money in your pocket and less "debris" to clean up. Even foam planes can be damaged with no problem. And probably the biggest factor in all of this is SAFETY. If you have no clue how to get started, the first step would be to see if you can join a local club. This isnt like kite-flying where you go and thats it. You can definitely injure yourself and others if your new to this hobby. I know its sometimes hard to ask for something you feel like you can do. But believe me its a little different with R/C planes.

Something to think about:

1. Foamies teach good mechanics but not all flight dynamics.
2. Theres no such thing as an indestructible plane.
3. If your fine with electric thats good but when your son starts hearing the sounds of glow and gas, be ready. Its definitely something to shoot for.
4. The prettier the plane looks the harder it will be to fly!