Do make mention that it is an anniversary trip when you make your reservations and again when you check in. Some nice little touches may be left in your room.
Also, when you dine at some of the nicer restaurants...mentioning that it is an anniversary trip when making ADR's there are often some nice touches.
As was mentioned before, we received champagne flutes from Cinderella's castle. They make up a special menu and gave us a champagne toast at Artist Point. Other restaurants also offer nice touches.
If you go to Victoria and Alberts, every visit is special, but you get a personalized commemorative menu with your names and the event on it, and you could get a special desert as well....in addition to a fantastic meal together.