ITunes U with non-Apple devices

You might want to look at Calibre. Famously one of the ugliest Mac apps ever created (although it's much nicer looking now), Calibre is an e-book manager. You can use it to process your books, categorize them, tidy up the metadata etc. and then hit "send to device" to copy the books into iTunes.

I originally used it because my ePub collection for my Sony Reader was in it, and so it was the easiest way to get that to my iPad, but I've stuck with it because it has lots more features than iTunes.

Simple.

• Use one AppleID for purchasing.
• Use one or many computers to download this content. Remember that iTunes can sync apps to computer A and music to computer B and photos to computer C. Each person can decide to join the communal computer for App syncing / backup / downloading without it affecting their Photo browsing.
• If they each get an iCloud account and use it for the rest - they can use the iCloud software on their PC to get the pictures or sync manually like any other photo device connected via USB.

I haven't tested it, but WiFI sync might also be available on the PC side of iTunes. Good Luck! Let us know how you fare...