Have you tried Airbnb yet ?
This option is a great one, for when you want to be immersed in a culture and are travelling with a large group. We enjoyed staying at this airbnb when we were road tripping in Tuscany, they are a little out of the way, but well located for many of the spots like Siena, Firenze etc.
We were one of their 1st bookings back then , it appears they are still on a winning streak with lots of amazing reviews, its a little on the expensive side at $750 a night but can accommodate 14 guests has a great view and pool, and the hosts are super friendly.
I have to say as well that just down the road from this place is one of the most amazing restaurants i have ever dined at ever, in the middle of nowhere ..called Il Paese dei Campanelli
We can help with flights and planning a Tuscany Adventure our team has extensive local knowledge and we have folks on the ground there who are locals.
So click on this link to check it out.