Ahoy Mahua!
I just returned from a magical voyage aboard Disney Cruise Line and packed mostly summer attire for our sailing. It was a bit breezy on deck one of the days, but for the most part we spent the day time in our bathing suits, shorts and t-shirts! At night, you will want to dress up a bit more for your nightly dining rotation in the main dining rooms. For your seven night sailing, you can plan on four cruise casual nights, one pirate themed night (or cruise casual), one semi-formal night, and one formal night. In the Planning Center Section of the Disney Cruise Line website you can find a very helpful
Packing List for your Caribbean sailing. I would suggest packing a sweater, wrap or light jacket for the evenings because it can be cool on deck or in the public areas of the ship.
I hope this helps, Mahua! Please let me know if you think of any other last minute questions!
Best wishes for a magical week aboard the Disney Fantasy!
Nancy