The pirate menu is the dinner menu in all three dining rooms instead of that restaurant's usual menu. So on the three night cruise, you would not get to experience all three restaurants' menus. We were LLAP on the Wonder in January, so we had the Lumiere's menu on the first night, Pirate menu leaving Nassau, had the Animator's menu the third night, and finished the last night in Parrot Cay with that restaurant's regular menu.
The buffet looked heavy on desserts, not sure what else other than turkey legs were around, and they Scoops open late during the party, so we just go ice cream and skipped the lines.