We do not advise the stiff suitcases, prefer the flexible suitcases which will be easier to tidy up in the catamaran.
Take the minimum of clothes, because most of the time during the journey, you will simply wear your swimsuit.

There will be multiple occasions to go ashore to spend the night on the islands of the Caribbean, but the dress code is not strict. Only a few occasions will appear to wear a dress or to be in heels, excepted maybe in Saint Barthélémy or Antigua.
Do not forget to bring a light jacket to use as a wind break; this will cover you in the evening on the dinghy.

Sports shoes or rubber are the most worn but pay special attention to the fact that none dirty the boat. Otherwise please move barefoot on the catamaran.

In summary, bring some T-shirts and a polo. For the rest, the decision belongs to you.
Sheets and towels are supplied with the boat, as well as the snorkeling equipment.