You could call, but I agree that you wouldn't want to lose any reservations and the table size needed for a party of six vs party of five is about the same. The problem you might run into is that some venues won't seat you until your whole party is present and they might consider it a whole new reservation to change numbers at the desk-- though that seems exceptionally rude and I doubt they would actually give you any problems.
The other thing is that I've heard Disney accepts ADRs according to any restaurant's given crowd capacity and your one less person might allow for another party to be seated, number wise. Though that's probably a stretch, considering it's only person. So... the right thing to do is probably to call but the wise thing to do might be to just mention it on arrival. And of course, we're overthinking it because we're Disney fans and talk about such things. Most people would probably just change it on arrival. We'll see what some others say because like you, I am torn.
Last trip: Dolphin, March 2013
Past Stays: Contemporary, Grand Floridian, Polynesian, Beach Club, POP, POR, Dolphin
1990 August Honeymoon - Grand Floridian
Delighted Disney Return Guest since 1981
Last edited by SBETigg; 12-06-2010 at 10:53 AM.