I'm saving that for next week. ;-)
(seriously.)
It's really very simple for a child. C-x C-s, C-x C-c, and arrow keys. All they really need to do.
I thought about vim, but I think it would lead to too many confusing situations.
I have a printed "cheat sheet" up there for the boys. It has commands and keyboard shortcuts. They sometimes forget it exists, but at least Jacob can read and follow directions on it without any trouble.