I would sync your iPad to the PC with the apps and the music, then sync only the movies with the movie PC ( this can be done if you choose not to sync movies with the first PC), sync the wifes email through mobile me? If she uses gmail this is definitely doable. You can have more than one email account on the iPad just set it up under Settings - Mail,Contacts,Calendars.
A little more information from you on the particulars would be needed to justify what I have said, but it may all work.
There is also a few movie streaming apps on the app store like AirVideo if you are not able to sync the movies or want them to take up space on the iPad.
AirVideo will not however allow you to stream drm protected movies, but the streaming is excellent in both quality and speed, it also does conversion of file formats on the fly. That way you can keep the movies on the movie PC and all you would need is a small server app that streams from a shared folder or folders.
Good luck