Oh junk, varied opinions is soooo right...
I pack wwwwwwaaaaaaaayyyyyyy too much every time I cruise (having been on five, I should have it down by now, but not so much...) I pack a different dress for every night, plenty of shirts and tank tops and shorts, way too many shoes, bathing suits and a cover up, and casual dress up clothes for going out after dinner. But I love dressing up and like to look super pretty for dinner-makes me feel like a princess
I've never counted how many times I have changed in one day, but I'm guessing around 3... lol
Dress capris and a nice top are fine for dinner, and you can wear them with heels or flip flops. Or dresses. Or sundresses. Really whatever you choose (minus the teeny tiny mini skirts and too small tops many teens i have seen wear...)
Dress to be comfortable. And remember you don't have to go to dinner every night-there's always the buffet on the Lido deck (though dinner is always a ton of fun if you're seated with good company and have good servers!)
Most importantly, you're on this trip to have fun. Be careful and have blast!
(You'll like the Holiday-I've been on it before and a girl I work with is engaged to a guy she met on that same boat!)