Here is the official word I received today:
There are two Captains parties. One is on the 1st formal night. On Fantasy and Spirit class ships it is still held in the traditional way in the theatre. Drinks are $1 off. On Destiny, Conquest, Splendor, and Dream class ships it is held on the promenade. Drinks are $1 dollar off.
The other Captains party is called the Farewell Captain's party and is held on the last night of the cruise. Drinks are free. This party may not have trickled down to all ships yet.