One thing that you will find is that the dress code is not enforced in the main restaurants. You will see people in shorts and t-shirts, for example, which you're not supposed to wear.
However, if you're like me and you actually
like to look decent at dinner, then most nights are "cruise casual". For men, this means long pants and a collared shirt. I usually wear khakis and either a pullover shirt or a "Hawaiian style" shirt. I usually wear a nice pair of sneakers, only because I can't pack 2 pairs of dress shoes, plus sneakers, plus sandals, plus beach shoes. Just not enough room.
This is how I usually dress for "cruise casual". This is not actually
at dinner, but it's me on my way to dinner, posing with a celebrity:
There is also a formal night and a semi-formal night. I wear a tux on formal night and sometimes also on semi-formal night (because the servers are pretty dressed up, even on semi-formal night). I think they say that a jacket and/or tie is sufficient. But again, you will see people in shorts and t-shirts, even on formal night.
I wear the tux to Palo for dinner. I don't know what the dress code is for brunch.
Here's my wife and I on formal night in Parrot Cay:
The costume night is "Pirates IN the Caribbean". You'll see a very wide variety of dress. Some people ignore it completely (like my dad), some go all out and dress as Jack Sparrow or a wench, and some just wear the Pirate bandanna that they give you onboard. I'm not a big costume guy, so the most I do is wear a Capt. Jack hat.
This is usually the extent of my family's "dress up" on Pirate night:
However you pack, have a great time!!