I need good anniversary surprise ideas that can happen in a plane?

My family is going on a vacation soon and we are flying back on my parents' anniversary. I want to give them a surprise by doing something special on the plane. Any ideas? I can definitely call the airline and have something arranged, but I don't know what to do yet. Thanks for any help!I need good anniversary surprise ideas that can happen in a plane?You should see if they can say something over the intercom or let you do it.