Have you considered some sort of classroom seminar, held shortly before the first snowfall? With such timing, you'd be able to help first-time winter cyclists determine what they'll need for the winter. They can then prepare for winter riding before the first snow hits. Even those of us who have been riding in winter for a might want a brief refresher. It's also a great way to let people know of any new products that might help them. This would also be the time to get contact information for those interested and get in touch with them for a winter ride the first Saturday you have snow on the ground.