Mandrake would be a really good choice. Its got alot of GUI interfaces, so you won't have to deal with the command line all that often but its something I would recommend highly to familiarize with though.
You'd be suprised though, most younger kids pick up on things faster than adults, so him using Linux, he'll be more inclined to pick up and learn probably rather quickly.
Also, if you have internet access, just read all you can ( lots of information on the web ), come to sites like this when you have questions as anyone here is willing to help out and etc...
In terms of programming, I would say maybe at 11, start out with some basic web design. Possibly HTML would be a good start for someone that young. Then move up from there if they show interest in it.