Lucca and pisa in one afternoon doable? Also what is driving like?

I think it's doable, more or less. Use Google maps to plot your route. Pick up your rental car at noon, it will take 45 min. to get to Lucca. Add about 1/2 hour for leeway, getting out of the airport parking lot, finding parking on the edge (outside the city walls) of Lucca. Maybe 2 hours in Lucca, including lunch. I liked Lucca, so I'd want to spend more time there than just two hours. About 35 min. to Pisa, add time for leaving Lucca, finding parking on the edge of Pisa. Spend an hour in Pisa, let's say. Your only logical route from Pisa to San Gimignano is on back roads. Probably very pretty and somewhat tedious. Many places in Italy don't offer an early dinner, assuming you mean early is earlier than 8 pm. Assume everything will take longer than you think you will, including extra time because you're enjoying yourselves. Which crazy drivers? In the cities, IMHO Italian drivers are more aggressive/assertive than many U.S. drivers. But if you've driven in Boston, for example, it will be business as usual for you.

After Pisa I would take the SuperStrada to Florence, directions in the RS books, then loop around Florence and follow the well worn route to San G. It shouldn't be bad as long as you don't start homing into Florence in the way. I'm glad its you parking in Pisa and not me.

@Nigel: there is a gigantic surface parking not far from the Campi dei Miracoli, with easy access from the FIPILI highway. I don't see what problem is there about parking there.

We drove into Pisa early and found parking easily, walked to the Field of Miracles, had a look around (didn't climb the tower, but checked out the Baptistry and Cathedral) for less than two hours. It was a pretty quick and easy visit. We stopped at Lucca but weren't impressed. The wall- turned-park, which was the best thing in the town, was decent but not great. The town was flat rather than a hill town, really nothing special. I can understand it for people who have mobility issues and can't negotiate hills easily. I guess it's also more convenient by train than other towns. It may be less packed in the high season (we were there in October and it was empty) but that would be directly related to how attractive the town is compared to others in the area. Other than those reasons, I can't see recommending it. Driving to San Gimignano is easy enough. There is a parking lot directly across from the front gate, and probably others if that's full. I think Italian drivers are aggressive but they will always let you in, they're just impatient if you don't take the opportunity they give you. In the cities you notice curious ideas about what red lights are for but otherwise it's no different than driving in crowded streets anywhere. I had fun driving and made it through without any scratches, dents, or (more worth worrying about) car prowling while parked.

Thanks all it seems like it should be doable... we are going to have a hard time with diiner as we are early to bed and eat early... perhaps we will buy some items to take home with us as most places we are in are apts.
I wonder how difficult that will be Dinner at 8 is way to late.

Barbara, you can eat earlier than 8 in Italy, it's just not always the nicest restaurants (but still good food), and the number of restaurants is limited. It may just be a cafe, but hey!

Read Rick's tour guide for Pisa in ref to seeing the sites. If you want to climb the tower, as soon as you get into that area, go to the ticket booth to buy your tickets. It's generally a few hours wait during high season. Otherwise, you can look at the tower and buy tickets to go into the Duomo & Baptistry. There are cafe/restaurants in the area and, of course, lots of souvenir stands.

Barbara, the larger or further north or more touristy the town, the less strict the 8 PM dinner start is. Why, in Milan, I think some places open at (gasp) 7 PM! And in Florence, I remember some places opening as early as 6 PM; there were only tourists in there at that hour, and it was only the places that fished for tourists, so not the best ones. If you really want to eat earlier, you will have to plan. Small grocers are open in the mornings, but not during the afternoon closing (1 PM to 4 PM or so); I don't remember if they reopen in the afternoon. Larger supermarkets, if you can find them, will be open without a midday closing, but they're not as easy to spot in the centers of Italian cities as in some other places. Having an apartment will make things much easier, of course, as you can stock the pantry and fridge when food stores are open, then make your own food on your own schedule. As said, you can eat in a bar (which in Italy is not a drinking emporium, but closer to what we call a cafe). However, you might be eating the lunch leftovers. Italians really do eat dinner at 8 PM, not 6 PM, so finding good sit-down food at the earlier hour is difficult. Don't discount the option of having a snack (like gelato, or something picked up from a market or bar) in the late afternoon, to tide you over until an 8 PM dinner. That's what I often do.

Thanks for the suggestions We do dinner early as we need to wait two hrs before we go to sleep (stomach issues) and we tend to sleep early so usually do dinner around 6 -6:30 but as you say having the apt will help with that...