We were there in late June, and story telling was at 6:30 pm.
It is just like the OP said, you sit around the firepit and a CM tells a story. Our CM was Melaine and she was great -- super animated while telling the story of and Uncle and Nephew Wolf. DD was captivated.
I don't believe you have to be a guest. They also play games in the evening, but they were too hard for my DD (she's 6). It involved using a book to identify animals, and we had just gotten there that evening, so we were not familiar with most of the not-so-obvious ones.