Susan..

From my own experience of trying to FIND people to play with in a very rural area, I think I would wait on the workshop until you have a core of people that are comfortable with each other. It is surprising how shy lone pickers/singers can be about getting together, sure that everybody else is better than they are (haha..not ME, of course!). And the idea of a workshop, the formality of that, no matter how informal it might actually be, might put these folks off...

If I weren't so isolated (and alone) I'd try something like this myself... Good luck!