Hi, Deanna!
Congratulations on your upcoming cruise! I know that you, your family and your friends must be getting so excited!
Photos taken candidly or as portraits from photographers aboard Disney Cruise Line ships keep track of your digital photos using your stateroom key (Key to the World Card). Therefore, when you take photos, you'll want to have the photographer "register" each photo with each family's stateroom key. When you go to Shutters to look, you will simply find your printed photos or look them up by scanning your stateroom key for your proofs' location or to look at your digital photos on an available kiosk.
There will be times when you won't be with the other family with whom you're traveling -- and sometimes even your own immediate family. (My little one had an impromptu photo session with Captain Jack one evening while the rest of the family was finishing dinner!) Therefore, I would be surprised if you both wanted the same photos on a CD, and it would be difficult to have the same photos on both of your accounts. Does that make sense?
Various photo packages are available that both families might consider purchasing together, and you can visit Shutters for more information about CD writing services. They may have more ideas about how you can combine your memories!
Have a wonderful day and a magical vacation. Bon voyage!
Andi