I was a chaplain at a retirement center (chaplains do many things), and we made lap quilts. I like the idea of baby quilts. Some of your quilters will be well experienced and some will just be starting. The treadles will help with memory association. So would material of different textures. Maybe mix squares of minkee with regular cotton, or make flannel quilts? The men might like making "rugged" quilts of flannel shirts, plaids, etc.
Are you thinking of placing a frame and a quilt that needs quilting in the room? That would be a great community conversation/friendship starter. If you get those stab/stitch double needles that just go up and down it should be better on arthritic hands.