We were at WDW for our 20th anniversary. Even though Boma has the buffet, the server let the chef know it was our anniversary and they brought us a dessert tray with Happy Anniversary spelled out in chocolate

We also got a happy anniversary card signed by most of the staff at BOMA.
Le Cellier did something similar with their dessert sampler. The extra magic here revolved around my DHs wedding ring. He had to have it repaired, so hadn't been wearing it. I snuck it to the jeweler, got it fixed and then snuck it on the trip. When we got to LeCellier, I excused myself to use the ladies room and found our server. I told her I was going to order the dessert sampler, but could she make sure that she placed it in front of my DH and would they put his wedding ring on the plate?
When the plate came out, not only did it have the ring, but Happy 20th Anniversary in chocolate syrup. At first glance, DH thought the ring was a decorative one and started to comment on how cool it looked, then he realized it was HIS RING!!
I would suggest that you ask that your anniversary be put on your ADRs, mention your anniversary when you check in at the restaurant and get the Happy Anniversary buttons. Even if you just get good wishes from the cast members, it is a ball.