1, It's a good idea to give them Linux if they agreed to it and have a general understanding of what is different.
2, I installed Debian on my 81 years old friend's shitty old laptop (it was out of curiousity), he never called me back to fix his OS. For your friend though, I'd recommend Linux Mint Debian Edition, as it feels faster than regular Mint.
I haven't tried the new update, since there were perfomance issues (in full screen the game didn't start normally I guess). How do you manage your leaders? Is it a quality-over-quantity upgrade?