The best motivator is recognition. Kids don't care if a language has books and whether there "exists" a game development kit. They only care about how much satisfaction they will get by learning something and building something with it.
If you want your kid to learn programming, the best approach is to teach them Swift or Java, or Javascript, so they can build a mobile app or web app and show off to their friends. And they will get the joy of building something that is actually used by others. That's how you get people to be interested.
LISP won't get you anywhere in that sense. Sure you may learn some programming concepts, but the ROI is not worth it. Kids might as well spend a bit more effort to learn languages with more exposure and actually feel the satisfaction of having real users.
That's basically child abuse.
Do you want your kid to learn actual computer science, or do you want him/her to basically be able to create a cookie cutter mobile app?
This is exactly the point I was making in the ancestor thread. If you want your kid to learn computer science, you don't force feed him/her things they will have no interest in immediately. Instead you teach how to build a "cookie cutter mobile app", and they will get interested and go from there and teach themselves racket or lisp or whatever you originally wanted to force feed them.
If the goal is for a beginner (whether child or adult) to be able to make cool things fast, Lisp is a great choice. The interactivity and the simple syntax makes it very easy to get up and running compared to more mainstream languages.