As far as I can tell, the version of ubuntu on the desktops is old enough that (some of) the software repositories aren't online for it any more (I can't remember which version is installed - I can confirm this on Wednesday). If this is the case then we'll need a newer version installed - I think the least controversial option would be the most recent ubuntu LTS version.
A less straight-forward choice is which desktop environment (de) to install (in ubuntu speak, which "flavour"). The reason I bring this up is that the default ubuntu desktop environment (gnome3?) is pretty alien to non-ubuntu users (and I say this as a long-term linux user!). If we put Xubuntu on instead (and so used the XFCE de) then it's a lot closer to a typical de, albeit still some distance from win or mac. It also has the benefit of being very light weight.
In part I suppose it depends on who the desktop machines are for. However, my personal view is that win, mac, and non-gnome3-linux users will find gnome3 odd. What are other peoples thoughts? If it's agreed that looking at different des is sensible, then are there any other contenders? Of course, it might just be me!
(I'm happy to install, or help install, whatever is chosen)