OK, I am a Diamond Class member and have never cruised RCCL, it's because of Celebrity. I am wanting to book to COCO Cay now (thanks Sony!)
I think I am understanding the many many ships of RCCL, I take it Freedom Class would be the biggest and newest except for Oasis and that Sovereign would be the oldest and perhaps smallest, am I correct?
The Sovereign is gone. It left the RCI fleet last fall. However RCI still has two Sovereign class ships - the Majesty and Monarch. Small cabins and high passenger density. The Monarch replaced the Sovereign on the 3/4 night runs out of Port Canaveral. Majesty is still going out of Miami. These are old ships in today's market.
Coco Cay is a nice little island but I wouldn't get too worked up over it. Mostly it is 100 acres of sand and scrub brush, along with a few open air shacks as bars and a buffet area. The beaches are nice but nothing I would call spectacular. It is just a nice little day at the beach with a pseudo-barbecue lunch (much of the food is cooked on the ship). More notably - the sea swells at Coco Cay can often be bad enough to force the Captain to cancel the visit. There is no pier and you have to tender.
I wouldn't choose a cruise with my primary focus being a visit to Coco Cay. You might be disappointed.