S32X_MiSTer VS Apple-II_MiSTer

Though it is worth mentioning that the MiSTer's 32X core still runs a ton of stuff at the wrong speed.

The issue you are describing happened to me when using some MiSTer FPGA cores.. it seems that the input video signal is out of range of the NTSC encoder (AD7xx): https://github.com/MiSTer-devel/S32X_MiSTer/issues/15

Yeah, FPGAs are so accurate the MiSTer's Apple II core can't even write to disk.

It looks like there's an Apple II core for Mister: https://github.com/MiSTer-devel/Apple-II_MiSTer

I also think a slightly different way to go here is an arduino kit. Even as an adult, I got some kind of ardunio kit with a bunch of parts that got me more interested in wiring & coding. I like it because it gives you the code and parts to get things working, but then, you have a bunch of stuff left over to expand on it. If you don't like coding, you can reuse the same code and build out the hardware, and vice versa. That is definitely more work and less play than Number Munchers though. You'll probably have to do some of the stuff with your kids, depending on how curious they are about this stuff. I've seen things that look like simpler arduino kits meant for teaching younger kids similar concepts, but I don't know how good they are.

I think a synthesizer is good, too. A cheap FM synth with a bunch of dials lets you play real songs, exercise your creativity and maybe learn some science skills by mistake like an old computer with a BASIC interpreter. There's probably software solutions geared towards infotainment as well.