They will all be "strummers," except an aoccasional harmonica player.
I foresee guitars, banjos, fiddles, basses, and mandolines. We might get a dobro too. My agenda would be learning to play along with one another on simple two or three chord songs, at slow speeds. here is what I have for community college setting:

1. Beginning old-time music jam for acoustic insturments, emphasizing
   jamming ettiquette and keeping time, chord changes, key structures
2. Emphasizing playing by ear. All will have vocal leads.
3. Play list of common songs (USA - South east: Amazing grace, You
   are my sunshine, I'll Fly Away, I am a Pilgrim, Keep on the Sunny
   side, Worried man blues.
4. Furnishing "guitar" music for above songs, with chord s and
   verses. If at community college, cost would be included in fee of
   $25.00 for five classes.
5. Let class run for five weeks, once a week, with all invited to
   free jams thereafter. Encourgae to join and play in local folk
   music association.
6. Jams after class would be slow speed, and would be with people
   sitting in a circle, with each getting a turn. Run about an hour.
   Encourage all to find other simple 2 or 3 chord songs.
7. Local community colleges will all run this through their mailings
   to all local homes, publicising it at their costs. Classes in the
   evenings.

Missing anything??