Italy

We rented a large villa for eleven through Chianti and More in Panzano. They specialize in Chianti and Florence so meet your requirements. Villas and Apartments. High level of excellent service throughout the whole rental process. We rented the villa for a week.
Our villa wasn’t in a winery but was surrounded by fields of grapes with it seemed local wineries down every nearby road. After we returned from our daily excursions , we would visit the wineries. Our son shipped a case home from one. Contact for rentals was Karin.
Friends rented from them and have had to cancel twice due to COVID . They were pleased with how everything was handled.

You may want to engage a travel agent who specializes in group travel. Eighteen people is not as simple as two couple traveling together. And a farmhouse may not be willing to commit to 18 without a substantial down payment and a contract. That is a lot of business at risk if you suddenly cancelled. Group travel is a very different business.

And Sep 22 maybe a little early. Some places don't get serious about reservations until about nine months out. And August tends to be a vacation month so who knows why you have not received any responses.