I've stayed at Casa Della Pia with my family, several times now and it never fails to impress.
Set in a tiny quiet Tuscan village with amazing views into and across the valley. The accommodation is typical Tuscan, well maintained and very clean.
Ideally you need a car to get there and explore although there is a bus service. Paul and Nadia, your host are incredibly helpful and provide excellent information including help with restaurant and activity bookings and especially the guided local walks. We ended up at an amazing local restaurant in the hills on one of the walks.
It's about a 30 minute drive to Pescia and about an hour to Pisa. After a hard days exploring, it was wonderful just sitting in the garden/terrace on an evening with a vino and watching the sunset... Bliss.