There's only two places. Cookie's Bar-B-Q and the one in the Adult beach area
The lines at the CC eateries go in waves. There are a lot of lines at Cookies, so if the closest ones are crowded, walk around the building. Parrot Cay on the ship is rarely crowded at all on CC day, and they have a salad bar and peel and eat shrimp.
There's only two places. Cookie's Bar-B-Q and the one in the Adult beach area
Neither of my kids ate on CC because the food wasn't available long enough. That's the only complaint we had (other than elevators). They did have sandwiches sitting out for a while after the food line closed. They even ran out of ice cream before my dd got there.
How packed are the ones on CC?
The adult beach is the place to eat if you do not have kids with you. They have steak, lobster tail, maui maui, grilled chicken and all the other choices you get at Cookies. It is so good. Not as crowded and more peaceful.
While we've heard rumors of the additional goodies, such as lobster, at Serenity Bay, we've not seen it on three trips. I suspect it's all on a trip by trip basis and you shouldn't count on it.
Last December, we came back form Serenity Bay and ate at Cookies (because it was so cold and windy...NOBODY was at Serenity) and the food selection was more varied. Lots of lines that move fairly quickly...lots of seating. Serenity Bay IS more peaceful and quiet...and the ice cream is much easier!