Welcome aboard, Lanning! I see from your previous questions that you'll be setting sail next year over Halloween for a spooky, yet magical, cruise on the Fantasy with your grandson! What fun!
One of the gift shops on the Disney Fantasy, Mickey's Mainsail, offers a huge selection of Disney merchandise for the whole family! You'll find quite a few pirate costumes and accessories for sale there, which are perfect to wear on
Pirate Night. From full costumes to accessories like eye patches, swords, hooks, Mickey Ear bandanas and more, you'll have quite a selection from which to choose! Many guests also choose to bring their own pirate costumes and gear from home, so that is an option as well. Don't forget to bring or purchase pirate gear for the adults too! Yes, on Disney Cruise Line, even the grown-ups get in on the fun of Pirate Night! have not seen prince costumes for sale when I've cruised with Disney, though on some sailings, I've seen adorable cruise captain outfits that little boys love to purchase in the gift shop and wear onboard. Just imagine the adorable photos you'd have with your little guy in a captain's outfit next to Captain Mickey!
I hope that helps as you continue to plan this exciting cruise, Lanning! Please let me know if I can help with any other questions before you set sail!