I have one kid using scratch now, and one older graduated to godot, roblox/lua, some javascript/web.
I would love to get them into lisp (already done a bit of Janet along with me), but it really needs to be something they can write their game ideas in, and share/show-off to friends.
From my own experience, it is absolutely possible to get good interaction with low latency in Racket, but of course as with any language you have to have enough experience to know how to avoid performance pitfalls.
For some of the gui work I've done I needed to mix threads and semaphores to get things to be really responsive when there could be a long running process triggered by a UI interaction, but in Racket it has been vastly easier and safer than in other languages.
Here is a library for making retro games: https://r-cade.io/
Ask on Discourse or Discord, for more game options.