Lindsay, jeans are just too warm for the Caribbean unless you are just referring to shorts for daytime wear. Evening attire is nice smart casual for evenings, informal like a dress or pant suit for those nights and formal as you wish to get on Formal nights. Short outfits or t-shirt & shorts with sandals or sneakers are great for daytime on board ship or on land. No swim suits in the dining rooms, but shorts are allowed at breakfast and lunch. You will want a cover-up for wearing over your swim suit from your cabin to the deck or even while at the beach on land. I have a great mini-dress which is easily worn on tours or on deck over a swim suit. Of ten cruises, the only room on Century that I found extremely cold was the Sports theme lounge near the theater. Bring a sweater or wrap just in case.
Bon Voyage