Welcome aboard, Charlotte! Congratulations on booking your Fantasy cruise for next month! There is so much to do on the ship and the Caribbean ports at which the Fantasy stops offer so much to experience as well. Your family is in for one very magical sailing!
Because the Fantasy's itinerary is a closed loop, meaning you begin at Port Canaveral and end back at Port Canaveral, you will not need passports for your children. A birth certificate for each will suffice. However, if you think you may use passports in the future, you may consider ordering these for the kids now, though at this point you'd most likely have to pay the rush fee.
Our family travels with passports for our children on these cruises because it ensures that if we were to have to stay at a port after the ship leaves, for an emergency or we missed the ship, we'd more easily be able to fly home from a foreign port. However, you are not required to have passports for this particular sailing, and many guests do simply use their driver's license and birth certificates for adults and simply the birth certificates for the children. See the
Proof of Citizenship information on Disney Cruise Line's website.
You only have a few weeks until you set sail, so please feel free to stop back with any other questions you might have! What an exciting cruise you have coming up, Charlotte! I'm happy to help, so don't hesitate to come back with another question or two before you head off on the high seas!