Hi Laureen:
Congratulations on your 20th anniversary. Disney World has a number of special restaurants to celebrate this milestone anniversary. My number one suggestion is California Grill atop the Contemporary Resort.
California Grill features delicious California Fusion cooking and spectacular views of the Magic Kingdom and the Wishes fireworks show. Other great grown-up recommendations are
Le Cellier, a tasty steakhouse at Epcot's Canada Pavilion,
Jiko at Animal Kingdom Lodge, which serves dishes influenced by African, Indian, and Mediterranean cuisine, and
Victoria and Albert's, a winner year-after-year of the prestigious AAA Five Diamond award.
When booking your reservation, note to your reservationist that you are celebrating a special anniversary. I would also mention the anniversary to your host when you check in and to your server. There is no guarantee anything out of the Disney-ordinary happens, but it's possible there will be some extra magic.
Happy anniversary.