Having a theme for writing can be a good way to push you into writing a song you might not otherwise, and maybe stretch yourself a bit in the process. But I've never been too keen on the idea of a theme when it comes to an actual song session.
And there seems something a bit strange about a "Folk Night" that specifically excludes traditional songs, and assumes that all songs benefit by musical accompaniment.
Still, if I was in Toronto I imagine I'd give it a shot.