I'd say don't patronise them by doing anything "dumbed down" or corny. On the other hand, don't try to educate them or impress upon them how "authentic" or "worthy" it is. Let them draw their own conclusions.

The first thing with any audience, but especially a non-folky one, is to entertain. Songs that tell stories, songs with easily pick-upable choruses or refrains, and songs with genuine humour. No novelty songs, interminable ballads, or "action" songs. And parodies are a waste of time if they don't know the originals.

Within those guidelines, almost anything from a typical folk repertoire should do.

Don't underestimate the audience. The Skids (a 1970s punk band) did an unaccompanied version of "And The Band Played Waltzing Matilda" as good as any I've heard in a folk club, and they were performing to an audience that at first glance couldn't have been less folky.