I salute you for your ambition and determination. I hope you get to realize your vision.

Now, as I read your question, I remembered an interview I saw a few days ago with Ben Kamens, one of the engineers working at Khan Academy, talking about scalability and things like how they manage their operation and the spikes of growth they have experienced in the past. It's a little light in technical details, but you may find it interesting: Root Access: How to Scale your Startup to Millions of Users.

One thing I'd like to mention is that when you hear someone else talk about the things they've done and how they have done it, it's easy to see it as an advertisement for a particular technology platform (AppEngine and other Google machinery in the previous video, for example), but that's not the thing to focus on. Whatever choices other people have made, the good thing is that their advice can be useful no matter what choices you end up taking. I know this seems like such a trivial thing to say, but evidence suggests that a number of people miss this basic concept, and then discussions quickly degenerate into pointless noise about concrete technologies, instead of the ideas.

I'd also recommend that you pay a visit to Google Developers youtube channel and type something like "scale" or "scalability" in the little channel search box. You might learn a few things from some really smart people who have confronted very real situations regarding scalability.

Best of luck to you, my friend.

I very much agree with what you're saying, and my recollection of playing Wolfenstein3D for the first time many years ago was indeed similar (although I also remember the not-so-pleasant diziness and head aches from the visual effects).

For more interesting nuggets about the impact of this game and the design behind it, make sure to check out this nice video of Carmack himself talking about the game and playing the game with commentary: http://www.youtube.com/watch?v=amDtAPHH-zE

I commend you for your genuine interest to aid your son now that he's starting to explore the exciting, wild, large, fuzzy, beautiful world of things we usually refer to as "programming".

There are some excellent recommendations for books already posted, but I just wanted to point out a video that might help you get a different perspective on what might be worth pursuing when teaching these things to young people: ART && CODE Symposium: Hackety Hack

It's a talk made by someone that has already been mentioned in other posts, a legendary figure that goes by the name of Why the Lucky Stiff (creator of the Poignant Guide to Ruby), and let me tell you, if you have already read something about him and felt curious about why he did the things he did and in the way he did them, seeing him on video really helps you see where he comes from and what his motivations are.

Make sure to see the bits of the talk where he presents a video made by a kid where he explains in his own words the experience he (the kid) had learning programming from books, and then trying to learn it from a sandbox like Hackity Hack (a creation of Why, but it really could be any other similar tool).

Best of luck to you and your son!