*Update*
My fourth grader acts interested in making a game, but can't get motivated to do anything about it. One of my second graders, however, drew up some pictures straight away! I'm going to take this short demo to him tomorrow so he can see that more graphics and gameplay ideas are needed:
http://www.youtube.com/watch?v=p-5TlCTmSNY
In other news... my fourth grader has me playing Doom 2. I never thought that would happen, but I find Doom 2 to be much more entertaining than Doom. He also told me to download Outlaws... and I have, but I haven't gotten around to playing it yet.