I agree with this. Start with something that works, and then show them how they can tweak it and customize it (heck, that's how a lot of us learned web developm

I agree with this. Start with something that works, and then show them how they can tweak it and customize it (heck, that's how a lot of us learned web development 20 years ago). If you don't want to show them games, maybe something like a fractal graphic generator or an N-body simulator might work? Or maybe there's something they're studying in science or social studies or whatnot that you could relate a program to?