We just returned from a four night Wonder.
We opted out of the formal night as we felt underdressed. so we ate at the optional restaurant Beach Blanket Buffet at dinner time (any time) and the food is just as good there.
As for the sting ray, my three kids enjoyed it very much. I actuallymade the ressies for the sting ray that same afternoon. Just notify the lifeguard who walkie-talkied over to the sting ray about our arrival. We were the only ones there for the 3:00 p.m. class so more one on one time with the rays and the teacher. Hooray. Afterwards, we took our snorkel gear and walked over to the first beach (in the family beach) short walk, 8 minutes and then snorkeled for the rest of the afternoon. It seems my kids REALLY loved the snorkeling very, very much. They were out there for about 45 minutes. Remember, there's a lot more fish and stuff to look at the first beach (the snorkel park) than the sting ray section.
Best to you. You'll have a GREAT cruise.