Ok.. this option is sort of out in left field, I know. but, have you thought of maybe a few conga drums, or bongos, or other shakers, rattlers, tamborines, etc. for the acoustic portion of the jam? I know that sometimes when players intend to play solely acoustic, they would rather a drummer sit out from the kit, or play accessory percussion instruments.
I have done small coffee shop gigs before, using a late 40's kit and brushes and/or Promark lightning rods (I think they call them that).. worked just fine. Key is, will the drummer playing with those fellas have the discipline to know to play very soft.