Siena/Florence itinerary help

I wouldn't necessarily disregard the prospect of staying within the city walls due to concerns about parking your rental car. We always found ample parking in the underground lot fronting the train station, which at 2 Euros per day was a real bargain. It's well clear of the ZTL areas and its location right on the SR2 made it a snap to head north up into Chianti or south into the Val d"Orcia every day.
Getting up into the town is pretty easy too - can either take a series of escalators inside the shopping area right next to parking and walk from there, or alternatively just pay for a taxi (about 12 Euros) for door to door service to your hotel.
For an anniversary trip a few years ago we stayed in one of the apartments at La Terazza sul Campo which we enjoyed immensely - spacious apartments with balconies overlooking the Campo. Can recommend it highly.
There's a Hertz office a couple of blocks from the train station that would make picking up and dropping off a car straightforward. Check their operating hours though - they can be pretty restrictive. As I recall they're closed on Sunday.
Other rental car offices are located a bit further away and would require a short taxi ride to get there.

We based in Florence last year and it was a fabulous jump off location. We stayed at the Hotel Opera, a smaller boutique hotel outside the city center, closer to the train station, and walkable into the center.

We did a day trip to Lucca. Loved it! Easy and quick train ride. We rented bikes and biked on the ramparts. We also explored the city and found the botanical gardens.

We took the bus up to Fiesole from Florence. The views up there are so worthwhile. It you are into history, the Etruscan ruins were fascinating.

We don't like to drive on vacation so we did a tour to Sienna, San Gimiagno and Pisa.

Enjoy!

Thank you Robert for your input! I appreciate the added details about parking options and getting to and from the hotel you recommended--it did open my mind up to possibilities within the city. The hotel, alas, doesn't have availability for the exact dates I wanted. I have decided since my initial posting to stay the additional night in Siena, making it 5 nights there and 3 nights in Florence. This will allow us to see/explore Chianti region on our way to drop our car off in Florence. Looks like we can drop it at the airport and take a 22 euro taxi into the city, which isn't bad.

Michele I appreciate your input as well, and am excited to see Lucca! I'm pretty sure we will try to do that.

But Fiesole does sound really interesting and lovely too! Even though we have one less day in Florence now, I'm wondering if it would be worth getting a very early start on one of our days and take the bus up there to explore even for just 1/2 a day, have lunch, and return to Florence for the afternoon? I want to do them both! :)

We returned from our Italy trip, which included 3 nights each in Siena, Pienza, and Florence a few weeks ago....... For your Siena Hotel consider Palazzo Ravizza. It is right on the edge of the ZTL but they have provisions for guests to drive there and park. You can take your car out once each day so you can enjoy day trips. Hotel also has good breakfasts and it is an easy walk to the huge piazza. If you stay there request room 1 which has beautiful painted ceilings..........We enjoyed both Monteriggioni and Voltera (good Etruscan museum). Did not like San Gimignano which seemed like a Tuscan hill town shopping mall and very few of those 14 towers are visible from anywhere in the town......Cortona would be another good day trip from Siena and has another excellent Etruscan museum.......We enjoyed the Chianti villages of Gaiole, Radda, and Montefioralle (near Greve), but if you have to choose, the villages around Pienza were lovelier. We skipped Montepulciano because it was VERY crowded. We mostly followed the RS Tuscany drive that day, but added a few extra roads......We found the little hill towns and the countryside much more enjoyable than Florence which was very crowded and also looked like they had fired most of their street cleaners......We returned our Avis rental car at the Florence airport. The return was easy, but it was very difficult to find the place to return the rental cars. Print out a map for that. Taxi stand right in front of the rental car return.....I hope this helps you have an enjoyable trip.

Thank you Cynthia for your input! I appreciate your hotel recommendation as well....it looks lovely, especially the gardens! Also good locale and parking option, so I see why you liked it!

However, since my last post I have actually found a wonderful AirBnB villa just outside of the city that I have booked. We can park there and either take a bus that stops right in front of the villa--5 min. and we're in the city. Or we can walk...so I'm happy with our choice!

Your endorsement (and others') regarding Volterra and Monteriggioni is affirming, and your honest assessment of San Gimignano is welcome, as--having seen it already, albeit long ago, I was debating about skipping it to have more time in the other 2 places that day.

Appreciate the mention of some specific villages in Chianti as well. Thanks for the heads up about finding the rental car place--I always program everything into Google Maps and will have GPS in the car, so hope we won't have too much trouble. Nice to have taxi stand right there to take us and our luggage into Florence! It's all coming together! :)