If you are looking for a truely memorible evening, Victoria & Alberts is the place. It is absolutlely amazing. It is very expensive, but its also included in TIW discount if you have one. We have been 2x, once on our honeymoon and then again last August. This December our night out will be Jiko since we are staying at AKV, and don't want to travel for dinner.
Also, if your looking just to have a fun time on a kids-free evening, you might want to try hitting the World Showcase at Epcot and try drinks from around the world, with a bunch of different foods.