I'm also interested in smartphone operating systems like Ubuntu Touch and postmarketOS etc.
- make sure bring extension chords, and make sure you have enough fast wifi for all participants
- bring enough USB-s. Installation on older laptops can take time
- ventoy is useful
- for beginners stick to Fedora/Debian. Popular distros come and go, but these two are constant and will be supported for a long time
- don't give options to beginners if they don't ask for it. You will induce paralysis of choice
- automatic dual boot setup by Debian installer works very well. Partition shrinking on Windows isn't scary as I thought before
- sometimes you can't install BIOS/UEFI drivers without windows (on older devices). You maybe want to do that before installing Linux
- i think it is good to have a windows installation ready. At least for windows boot loader recovery if anything goes bad
- bitLocker can be PITA. Don't lock users device
- after installation update system
- write some material, what-to-do-after-installation guide, and give to participants. Maybe create group on some social network or messaging app