IPhone does not show up on iPhoto anymore

What you’re asking is a hell of automation and it can’t be done “just” like that.

I suggest you try to make a combination of Automator and Smart Albums on iPhoto. Things you want to know about iTunes: EXIF is not preserved when Synced to iPhone through iTunes which is part of your requirements.

You could use a Smart Album in iPhoto and Flag the pictures you want to transfer then create another Smart Album with those flagged pictures and only transfer those (or vice versa). Use Keywords to your advantage. Consider a nice app like Keyword Manager for iPhoto to help you with that.

I have no idea why iPhoto makes you nervous, but you should be pointing at iTunes for that…

iPhoto is perfectly suitable for picture maintenance and sorting. You can later use automator to resize them and do fancy things (even tagging!). The same can be said about Aperture.

Your workflow should be, download to iPhoto automatically. Classify, Tag, Delete Bad ones, Adjust, Edit, and transfer to your devices for later viewing (and backup). If you just want to have a backup up of what you do, let Time Machine do it’s work with your iPhoto Library or add another step, use Image Import (or Cameras) to organize, then add to iPhoto for treatment and later transfer to your device(s). The original imported folder will be untouched and, eventually backed up by Time Machine too.

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...