Hi again, Mindy! I think you said you'd be taking a three-night cruise on the Disney Dream. For those sailings, you can see the
Travel Document requirements page on Disney Cruise Line's website. You'll see that for the Caribbean and Bahamas, a passport is not necessary, but adults need to have a state-issued driver's license plus a copy of birth certificate, or just the birth certificate for children.
That being said, my family always prefers and feels much more comfortable traveling with passports for each member of our family. You just never know when an emergency or health issue could leave you at a port and not able to get back to the ship before it departs. If that were the case, having a passport can certainly make it much easier to get home. We like to play it safe, so we do have passports even for the kids and keep them with us each time we go into port. If you have time, I, personally, would suggest going ahead and getting one. It's really up to you, though. Since you'll be sailing for three nights, there certainly is less chance of anything happening than there would be on say a two-week Panama Canal cruise, but again, it's up to you.
I hope that information helps a bit.
Keep your questions coming, Mindy!