Welcome aboard, Adina! You are about to set off on my favorite kind of Disney Vacation: a surf and turf trip including a stay a the Walt Disney World Resort and a magical cruise at sea with Disney Cruise Line! You're in for such fun!
The easiest way to make purchases at the park is with your
Magic Band. Purchases made by tapping your Magic Band will be charged to your resort room account and the credit card you have on file with them. Of course, at the parks and resorts, you are welcome to pay for any additional purchases with cash, credit, debit or Disney Gift Card. On the ships too, you'll be able to make charges by using your Key To The World Card which will charge your stateroom account and the credit card you have on file. However, on the ships, they operate on a cashless basis. Any purchases made onboard or at Castaway Cay must be made with your Key To The World Card. The gift shops onboard will also accept Disney Gift Cards. You'll want your credit card and cash for any purchases in port though, as well as for tips for any of the complimentary room service orders you might place onboard. It's traditional to tip a few dollars to the Cast Member who delivers your room service.
Disney makes it pretty easy for you to leave your cash and credit cards behind and simply utilize your Magic Band or Key To The World Card to make any purchases you'd like. I hope I've helped as you continue to prepare for your trip, Adina! Let me know if I can answer any other questions about your cruise before you set sail!