If you're going to stay in an agriturismo, you'll probably need a car (large for 9). When you head into Firenze for the museum day, you'll want to train in to avoid the ZTL (areas you're not allowed into with a car without special permission). With Pisa and outlets as destinations, you're somewhat split geographically. The big outlet mall (Leccio) is southeast of Florence while Pisa is west and a bit south. You might want to look for an agriturismo around Vinci which is southwest of Florence. Short drive to train into Florence, not bad drives to Pisa (I'd recommend Lucca over Pisa any day) and the outlets. Some interesting history as Vinci is Leonardo's birthplace...