I don't know if the cancellation policy is the same for lunch as it is for dinner, but we were just at the lunch in October. It was supposed to be me and both my DD's at the lunch, but my oldest DD got sick the night before and didn't go with us. I asked at the resort and they said that they didn't charge your card in advance, so I could just let them know at the desk when we checked in that my one DD was not coming. Which I did and I was only charged for my other DD and myself on our bill.
So I assume that they only ask for your card and charge you if you just don't show up. I could be wrong though since we still kept part of our ressie, but that is the impression I got from the resort when I asked.