Be VERY nice to the tavern owner. OT musicians and their audiences (as opposed to the bluegrass crowd) don't tend to run up much of a bar tab, and you're going to be dependent on the owner's good will to keep the jam going. Back when I ran one of these things in New York City about a generation ago, We kept the owner happy by holding OT jams on Thursday nights, when the bar would have been empty anyway, and concerts, which were mostly bluegrass or combined BG/OT on Saturdays, when we could get the owner more traffic and therefore more money.

Banjo ray is absolutely right about the incompatibility of BG and OT musicians in jams. The Washington DC BG and OT group holds biweekly jams and it used to (and perhaps still does) designate different spaces for the two styles.

Good luck, in any case. A good jam session is a delight and worth every bit of the effort.