I would like to be able to host MapTool(Linux Mint 12) as well as one or more virtual machines also running linux of some flavor on which MapTool will run for the players.
So the plan is to run multiple Linux VMs on top of a Linux host OS (Mint)?
Definitely use KVM (Kernel Virtual Machine) as it's much, MUCH more light-weight than the other solutions (VirtualBox, VMware, etc). I have no idea if Mint includes KVM support though.
The players would then connect to the virtual server(s) using product X (which is where the advice comes in) using either IPad or Android tablets.
So you want to run a GUI in those guest VMs and have the clients connect to it...
I don't think I'd go with full-fledged VMs, since that'll be a lot of overhead that you don't need. Instead, you can run an X server in a framebuffer configuration (i.e. RAM only, no physical display) and the players could connect to that instead. It's been a long time since I've used a framebuffer X server, so I'm sure the setup/configuration has changed. Essentially, the X server uses a RAM buffer (the FB) as the device and doesn't get the performance benefits of using hardware acceleration since there's no real hardware there. But that would have to be lighter than running a full OS in a guest VM.
Regarding the player equipment... iOS is not of much use to you because of Apple's death grip on the app marketplace (unless you jailbreak the device).
If one of the TeamViewer-like apps were open source, it might be interesting to modify it to work with specifically with MT, but that wouldn't be a simple solution.
That means Android or WebOS; I think Android is the more logical choice (for a lot of reasons). In terms of specific equipment I can't help there as I haven't used any of it.
Good luck! And I've love to hear how it works out!