I think the only dinner with characters is Goofy's Kitchen. I could be wrong, but I didn't think the princesses stuck around for dinner at Ariel's Grotto because it turned into a WOC dining package option. I think the menu is supposed to be pretty good at Goofy's, for a buffet. We did breakfast there and I wasn't totally impressed, but we paid their super high rate in cash. I wish I'd paid a bit more for dinner instead. The characters were Pluto, Minnie, Chip, and Dale, with a picture with Chef Goofy on the way in. We went on our last day, and by then we'd seen those guys a few times already, which is the only reason I am considering lunch at Ariel's for our next trip. Princesses! I do believe Goofy has the largest menu of all the locations, and the extremely limited menu at Ariel's is just not sounding appealing to me.
