If you call they can not just add one to your ADR. They have to cancel the ADR you already have and make a new one for the new amount of people, if one is available. I might call and have them check if ADRs for 4 plus one under 1 are available. If they are, I'd make them first then cancel the others. If they aren't I'd just go to the podium and say you had one extra. I had 1900 park faire for dinner once for 2 but really needed three. I was just going to cancel because three wasn't available. I went to the resturant to cancel and the restuarant manager told me not to cancel, just show up with one more. It was no problem at all
Shelly