I've sailed a couple of times over Valentines day. Mostly only saw some decorations, V-Day themed fruit carvings and the such.
However, one year on the Magic, and I think this was when Dreams was done on the last night, the main stage cast put on a really cool Valentine's Day cabaret in the Promenade lounge. The lounge was decked out with baloons and LED candles, very very nice. A bunch of the performers sang songs they chose and it was a special treat.