For my parents 50th wedding anniv 20 of us went to WDW. Here are two of the things we did:
1. At Chef Mickey's, the server had Mickey and Minnie come up to my parents to present them with a gift. Mickey actually got down on his knees and handed my mom a ring box. Inside was a ring with 15 diamonds---one for each grandchild. As a surprise for us, the server brought souvenier champagne glasses and champagne for my parents!
2. We were meeting at an offsite restaurant for a group dinner. All 18 of us showed up in matching t-shirts we had designed with Bob/Shirley, Mom/Dad, Grandma/PopPop 50th Anniversay on the front chest and a family tree listing each "branch" of the family on the back. It took them about 10 minutes to notice we all looked identical, then we gave them theirs and they went in the bathroom to change!
3. We also each took one morning and took Mom and Dad to breakfast just with our individual family. Our choice was 1900 Park Faire for brunch. The characters went nuts when they found out it was my parents 50th!
HTH!