I'd suggest some of the online emulators, like: https://skilldrick.github.io/easy6502/ or https://www.masswerk.at/6502/assembler.html The difference here is that these are pure 6502 and no hardware, which yeah does limit you but at least gets your feet wet, and more importantly, you see the status of the registers, memory, etc as you work with it, which isn't as easy on real hardware.

From there then you can perhaps choose a platform (Apple, Commodore, trainer, etc).

What would be really cool, is to see if maybe that first link works for you..have him write some code, then transfer that to a real platform, perhaps even burn a rom (if you can) and see it in action. I did this to test the ram on the sound board of a pinball machine that was 6502 based - had it turn on an LED if the ram was bad (it was). Jeff (aka Bags)