Ahoy there, Merijo! Thanks for cruising by planDisney with your question. Your 
Very Merrytime Cruise on the 
Disney Dream sounds absolutely magical. There’s nothing quite like celebrating the holidays at sea with Mickey and his friends!
Yes, you can absolutely use your MagicBand+ during your December cruise. On Disney Cruise Line, it functions as a 
DisneyBand+, giving you hands-free convenience during your voyage. If you already have a MagicBand+ from Walt Disney World Resort or Disneyland Resort, you can bring it along, just make sure it’s fully charged before you board. A crew member at the terminal will help activate it for shipboard use when you check in on embarkation day.
Here’s what your MagicBand+/DisneyBand+ can do on board:
    •    Unlock your stateroom door.
    •    Make purchases for food, beverages, and merchandise.
    •    Can used by kids to access the youth clubs instead of the Oceaneer Band.
    •    Link your cruise photos (including those taken at Castaway Cay and Lighthouse Point).
    •    Tap to embark and disembark the ship at ports of call.
    •    Enjoy a few extra enchanting surprises during select experiences!
While it’s super convenient, your Key to the World card still works for all of these functions, so using a band is optional, but it’s definitely a little more fun. And just between us, the bands are waterproof, but I’d skip wearing it while snorkeling at Castaway Cay (let’s just say I learned that lesson the hard way)!
Since you’re sailing during the holidays, don’t miss the Dream’s Tree Lighting Ceremony in the atrium on the first night. It’s a heartwarming way to start off your Very Merrytime voyage.
I HO-HO-Hope your holiday sailing is filled with festive fun, Merijo!
Sea ya real soon,
Eean