In reply to the "new" required documentation for Carnival, they have the info posted on their website, but here it is in short:
- a passport, valid or expired for less than 10 years prior
- original birth certificate
- state issued copy of birth certificate
- US military ID
- original naturalization papers
In addition, anyone 16 years and over has to provide a Photo ID in addition to the above. There is also a link on their site about birth certificates.
In reply to the dress code, we have been on 2 Carnival cruises (Sensation, Destiny) and we have noticed that for the Captain's dinner, people usually dress up more than the 2nd formal night. On the Destiny, it seemed that the whole ship was dressed better than other cruises we have been on. On formal nights, Carnival was strictly enforcing the jacket & tie for men. It seemed that as long as women were dressed nicely, there wasn't a problem. Pants suit, or skirt and blouse or formal gown -- anything goes (just don't wear jeans and a t-shirt).
For casual nights, Carnival isn't that worried about how you dress. Our teenage son was with us on one cruise and he wore a t-shirt with a Hawaiian shirt over top and khaki cargo-style pants. The Hawaiian shirt was worn on quite a few nights and nothing was ever said as to how he was dressed. For formal night, however, he wore a dark suit and tie. A blazer and tie would work, too.
I know with my first cruise I was so worried about how to dress in the evening until I saw a friend's cruise photos. For formal night, she wore a 2-piece black pants suit with a white blouse and her husband wore a jacket, dress pants and tie. After that, I never worried again.
Hope this helps. Enjoy your cruise!