Linux tends to require configuration/debugging from the console. Don't get me wrong, I use linux every day, but I would never push it on someone who is not interested in solving their own tech problems.
If it's setup and working it requires no configuration/debugging. And it sounds like whether it's windows or linux he's going to be responsible for fixing any computer problems so it may as well be on a platform less prone to problems that he can fix better.
Just being on a platform where uses can't get infected with malware from stupid flash game sites cuts out 90% of maintenance.
