Sigh. After much discussion at home, it has become clear that what my son wants is the green version of the one from Performance Bikes. He has no desire for anything else. I'm going to start with that, take him to see it, and then if he doesn't like it, we can work up to the Trek.
Still, I maintain that he needs a better bike than that.
I may take him to try out some BMX single-speeds first, so he can feel what those are like too. Great idea on that.