Hi, Lori!
Presently, all travelers -- including U.S. Citizens and all foreign nationals -- are
required to have a
valid passport to enter or re-enter the United States
by air. Therefore, Disney Cruise Line strongly suggests that each guest hold a valid passport. In the unlikely event that you experience a family emergency during
your cruise and need to return home via air from a foreign port, you
would already possess the appropriate identification needed to travel.
As of two years ago, all U.S. citizens traveling outside of the U.S. are
required to have proof of citizenship to re-enter the U.S. This is true if the
cruise enters any
foreign ports. At this time, proof of citizenship can be a
birth certificate in combination with a valid U.S. ID (such as driver's
license).
Also, feel free to disembark in Nassau and at Castaway Cay. You'll simply need to keep your IDs, birth certificates and stateroom keys with you as you visit each port. I hope that helps you plan.
I'm glad that you like the panel! Have a wonderful day and a magical vacation. Bon voyage!
Andi