Ahoy Heather!
Thanks for sailing by planDisney with a great question!  When I sailed on my recent Disney Cruise Line vacation, I loved the convenience of 
DisneyBand+ - both on the ship and at 
Disney Castaway Cay.  Heather, I'm happy to share that I was able to purchase some great souvenirs on Castaway Cay with my DisneyBand+.  Whether you're searching for a beautiful new Spirit Jersey or some fun beach toys (or anything in between!), there's plenty of shopping to enjoy!  After finding a perfect little Disney Cruise Line bath toy set for my youngest, I was able to pay with just a quick tap of the wrist.  
During your trip, you'll find that your 
DisneyBand+ can be used for much more than just making purchases.  It's a great hands-free option to 
enter your stateroom, and if you're cruising with any younger sailors, they can even use it to 
"tap" into the Youth Clubs!  Much like MagicBand+ in the Disney parks, you'll also find your DisneyBand+ will light up and interact with select shows and entertainment during your sailing.  Speaking of the theme parks, you'll also find your DisneyBand+ can be 
used at both Walt Disney World Resort and Disneyland Resort on future visits!   
If you run into 
any issues with your DisneyBand+ or need help activating when you arrive at the port, a Cast Member will be happy to help.  I needed a little extra assistance getting mine activated, but they had me ready to go in no time at all!
Heather, I hope this information has been helpful and that you enjoy a wonderful cruise!  If you have any other questions, please stop by to see us again here at planDisney - we're all ears!
Happy Holidays and Bon Voyage!
Kristi