Just some additional thoughts:
Your formal night will not be your first night--you would have time to ask your waiter about this in advance. Because this is important enough to you that you are having a bottle of Cristal, I would suggest that you do more than cross your fingers and hope for the best. Find out whether or not your waiter will/is allowed to serve this, whether he would be ok with the gray area of putting glasses on the table and having you do it (unlikely?). If he must enforce rules, this situation will put him and you in an uncomfortable position.
If you find that it will not be possible to have this in the dining room at dinner, why not plan on having it in your stateroom before dinner? In advance ask room service to bring 5 champagne glasses to the room, then put them along with the champagne in the refrigerator to chill the day before.
I don't think you will need a champagne/ice bucket because there are five glasses of champagne in a bottle. Beware of asking room service for an ice bucket---you will be presented with a cheesy plastic bucket with the Coors Light logo on it. I adore Carnival.