Everyone checks in 30 days out, so you'll all be able to check in at the same time. The advice in this thread (especially having all photos saved on both your computer and your phone, and having a document with all the other info typed out already so you can just copy/paste, were lifesavers for me. Also skip as much as you can (just select cash for onboard account, skip entering flights, etc.)-focus on the photos and the demographic info. You can edit onboard account and travel plans after you get a PAT. Also, watch the date formats-I was trying to enter birthdates and passport expiration dates and it kept defaulting to today's date for some odd reason (I think I had the year formatted wrong). But it won't tell you that right away, it'll just spin/load for a while then tell you something was wrong. So the extra few seconds spent to check all dates are correct before you hit submit will likely save you time having to redo (after a wait).
I believe you will choose PAT by stateroom. So if each family has their own stateroom then yes, theoretically, they could all have the same PAT. If you can get someone to help you with check in (since you have five rooms, you can work on room 1, someone else can work on room 2. The more you can do simultaneously the better chance you have of getting the same PAT for all 5 staterooms.
With that said, you are able to edit your PAT, so if everyone doesn't get the same PAT you can change it later. Or, just have everyone show up at whatever the latest PAT is-at a certain point, they'll call open boarding so PAT/boarding group might not matter anyway.
Good luck!
