For our dd6, we took one Belle dress for formal night and then an adorable Minnie dress from the
Disney Store from Easter for semi-formal. We also took a pirate costume. She really enjoyed dressing up and many of the little girls wore their gowns (particularly on formal night). I just rolled all of her stuff into ziploc bags and still had plenty of room. I'm afraid if we didn't take one or two costumes with us, the temptation would be too much at the gift shop
We still ended up getting the Minnie sailor suit dress.
The pictures are priceless. We have one of her with Cinderella which is amazing. She also loved how people referred to her as "Belle" all night.
I'm in trouble for this year's cruise... she wants to bring MORE costumes! Ugh!