They don't leave until tomorrow.
Reservation is not until Sunday.
I can't believe there isn't a way to do this. I'd rather not just give them a gift card...I'd like the waiter to present them with the bill and says it's already been taken care of.
My MIL did that for us for our 10th anniversary (not at Disney) and 20 years later, I still think it was one of the nicest surprises!