Hi Leeg
As long as you save documents in Microsoft's version of open XML then you should be fine sharing docs between your Windows PC's and WinMob 6.1 devices.
See
here for more info.
Just make sure that your devices come supplied with Windows Office Mobile!
In regards to your choice of device this very much depends on the objectives of using the technology, i.e. what outcomes you are seeking. You'll naturally need to consider what level of support will be available to teaching staff and how these devices may be embedded within learning and teaching practice.
If you're wanting to engage kids on their terms have you considered asking them what they'd prefer?
Cheers
G