When I went in early December, I had Disney dollars with me but had to use a credit card at the port, which they preauthorized a charge of $500. (There were two of us, not sure if the preauthorized amount changes with the number of guests in your party.) The credit card isn't charged until the end of the cruise, so if you have Disney dollars, you could use them on the ship at Guest Services to pay off your account (or use your charge, cash, etc.).