Keep in mind some shore excursions DO sell out quickly. If you dont have access to do stuff online, you're best to split your party up and have some people head for Palo ressies, another group to head for Spa ressies, and the last group to head for the Shore Excursion desk. This way you can cover all your bases.
You want to pretty much ignore them, too, when we're filing in to the ship as they direct us to Topsiders/Parrot Cay - Just tell them you want to get in line to make reservations - they will understand.