If you like to taste some Italian traditional food, then Il Camino is one possibility when you are in San Donato. I often go to this place to eat pizza but sometimes I want to have aproper meal, then Il camino has a wide variety of regional foods, mainly with Tuscany/Lunigiana fingerprint.
My favorite is the spaghetti alla costa smeralda where several types of fishes are used as condiment for the pasta and then is covered with thin pizza dough, befor the cooking is finished in the oven (spaghetti al cartoccio).
It is a family business, and the owner Ugo is always there for a good suggestion, just tell him your tastes. It is not cheap but the quality has a cost.