I put a large black "hefty" garbage bag over the suit (poking the hanger thru the bottom of the bag) and then gently fold it in half and place it on top of a suitcase that's about half full of clothes. It stays nice doesn't wrinkle that way.
We are bringing a 12 pack of soda in our checked luggage, wrapped in a sealed plastic bag. We are also bringing along 3 bottles of wine...haven't decided whether to carry it on or put it in the checked suitcase. This is NOT smuggling because both the Carnival website and our cruise docs say that we can bring a reasonable amount of soda and wine for personal consumption in our cabins (or if we bring the wine to dinner, then we'll pay the uncorkage fee). These quanities should be reasonable for one week for a family of 3.