I’m not sure how much time you are given and how much ‘hands on’ is desired, but you could buy a bunch of cheap, old, used desktops (that all use the same parts) and teach the kids what the various parts do (CPU, GPU, motherboard, PSU, SSD, RAM). Then have them build the computers and install linux on them.
Maybe pre-wire the PSU to most of the parts to save time during the build day(s). You may also want to have the CPUs pre-installed so you don’t get bent pins galore.
This entire idea would be massively benefited by a TA that could assist working with groups.