Chuck, found this elsewhere and pass it along fwiw. Not sure how old prices are or if occupancy limits have changed, but it may have been accurate at one time.
Private Beach Cabanas
Castaway Cay offers guests the luxury of renting one of 20 private cabanas. These 325-square-foot cabanas are divided between Castaway Family Beach and Serenity Bay Beach. On the family beach, the cabanas are located on the far side of the beach, offering a little more seclusion, along with a great view of the ship from the cabana's front deck.
Cabanas are furnished with cushioned chairs, chaise lounges, side tables and a dining table. Also included are a refrigerator, lockable storage unit, outside fresh water shower and a shaded deck. When you rent a beach cabana, you will receive non-alcoholic beverages, suntan lotion and towels. Other packages with special services, food and beverage options are available. For an additional fee, guests can also reserve the services of a private cabana host.
Cabanas can be reserved online ahead of time or at the Port Adventures desk while onboard the ship. They will hold a maximum of 6 guests. On the Family Beach, they can be rented for $549 per day.
The Serenity Bay Beach cabanas are $399.
A Grand Family Cabana is available and can hold up to 16 guests. The price for 10 guests is $966.43, but 6 more can be added for $53.75 per person. This cannot be booked online.