Leading an open jam

One of my bands is supposed to lead an open jam in a few weeks. It's our first time doing such a thing, and it's supposed to be an ethno-style jam... meaning, I guess, bring your baglama instead of your guitar. They've done those at that club before, they were just led by other bands. Hopefully we can do well and make this a regular monthly thing. I expect that unlike a jazz or fusion jam there will be less picking actual tunes and more "pick a key and improvise", but that's is not a problem for us.

Any advice on how to handle this from an organizational and logistical perspective? I guess play some of our regular songs to create some basic expectations of style, then take a break and talk to whoever shows up to see what keys and styles they're comfortable with, then invite them up on stage in "compatible" combinations while a few of the regular band members sit down?

 

Thanks, making a list of people is definitely a good idea. As long as more than two or three people show up, haha.