I could be loony, but I'd think acquiring the latest and oldest MacOS X you can would be sufficent, and a Mac for each. The next MacOS X update should be showing up soon (which is why I havn't bought a MacMini yet), so I suggest waiting for that. Something significant mouse related (I think) was added to an earlier version of MacOS X (10.1 or 10.2... I can't remember). I also can't remember exactly what that was (scroll button support or multiple buttons?)... so yeah, I'm no help.