We ordered the Birthday Celebration cake, banner, etc. for our son's birthday on our Feb 13-17th cruise. He was turning 4 on the 15th. The cake was in our stateroom when we arrived, and the banner and other birthday decortations were already hung.
The only mistake we made was that we had eaten so much food for lunch at the beach blanket buffet, we couldn't touch the cake by the time we entered our stateroom. Our son did eat the white chocolate "happy birthday" shaving of a cruise ship that was on top. It wasn't that large, but when we tried to stick it in the "cooling box," it wouldn't fit at all. I'm sure we could have cut it in half, but we didn't have anything else to place it in. After dinner that night, we were way too full to eat it again. We were afraid it may have been made with something that needed refrigeration, and not wanting to get sick, we ended up having to throw it out the next day.
On his birthday, the waiter did bring him a cake that was actually bigger and had the same white chocolate shaving on top. I'm not sure what kind of cake it was... something with a jelly type frosting. It seemed like just about every table in the restaurant had some celebration during the week and they all got the same cake.
My suggestion would be that if you are going to order it, make sure you'll be hungry enough to eat it. Let your waiter know the special occassion, and it will be celebrated when you want it without having to waste a whole cake.