I ate at 1900 Park Fare during the night of the first MNSSHP this year and both step sisters and Lady Tremaine (sp?), along with Cinderella and Prince Charming were present. We then watched the Hallowishes from the Grand Floridian (though I'd recommend another location for that, since even though the view wasn't bad, they didn't pipe in any of the music from the show).
I know you didn't ask about the experience there, but in case others were curious. The characters are very engaging and the food is above average for a Disney buffet (much better than Crystal Palace), but the characters all arrived in a clump, which meant that we were there for more than half an hour before I could actually eat. Beware if you're the designated photographer for your table!