Not sure about cancellations, but I would bet your chances of walking in might be better that at some of the theme park restaurants. I can envision a lot of situations where folks get caught up in what they're doing at the parks and either don't make it to the resorts or decide not to leave the fun for their ADRs. I'd go check it out for an early dinner. If you don't get in, it's still a nice monorail ride and chance to see the GF. Also, when we went the Fairy Godmother sat on a bench outside the restaurant talking to the kids. Not sure if she still does this, but if so you could see her without getting in for dinner.