Learning Win 8
I think you'll have to give the same service to people you convert from older Windows to Windows 8. Linux Mint has a similar GUI as Windows XP or 7, the teaching you need done there shouldn't be too large, people are used to this, things which differ mainly are the way software is installed, and that should be easy to teach/learn. On the other hand, moving from any OS to Windows 8 is a pretty large step, it'll take a large learning curve, so you might as well ditch it and use Linux instead. There is also no problem installing most distro's to an SD card or USB stick, so I don't see any difference there.
Why are you showing your users such an old version of Mint? 13 would be current...
