Need advice on how to spend 3.5 days in Florence

Your plan of taking the bus to Siena and spending the rest of the time in Florence sounds best.
IMHO, you probably don't have enough time to rent a car and try to see more than Siena and Florence. It would be physically possible but not sensible, IMO. When traveling in that part of Italy, sometimes less is more (covering less square miles or sights can lead to a better quality experience).
Renting a car in Florence gets complicated because of the ZTL's.
Florence might have more art/culture per square foot than any other place in Europe.

I agree with Kent. The only reason I would modify his advice is if you aren't as interested in Renaissance art. In that case, you could cut a day from Florence and spend it elsewhere. I'm not sure renting a car is worthwhile for such a short visit; in addition to Siena, buses go easily to Lucca and Pisa, among other places. Sure, a car allows a "whizz-bang" drive-by of several towns in one day, but I agree with Kent that by doing that, you "see" more places, but really see less.

I also agree. I would spend the time in Florence and you could take a train to Pisa and then bus from there to Lucca if you didnt' go to Siena. My husband and I did this on our second trip and Pisa was a favorite of both of ours. We traveled by train and bus. We have also rented a car from the airport when we had more time to spend driving around ... no trouble renting their but we used car to go to Volterra, Montepulciano and to visit family.

I was somewhat is the same position as you, and wanted to see a little bit more of the outside of Florence than Siena. We opted to go with a private tour company (Walkabout) and tried their Tuscany tour. It was a nice break to have someone else worry about the logistics of the day, and we got to see Siena, San Gimignano, a Tuscan farm/winery, and Pisa. So, that could be an option to consider. I think you would have time to spend one day outside of Florence, and the rest of your time enjoying Florence. Have fun!

I have a similar trip there next month and spending a similar amount of time in Florence. We'll probably do a Tuscany tour and let someone else worry about the logistics. The folks that run our hotel have a tour company, www.ijustdrive.us. They do a small group tour (max 8) of Tuscany that hits the same sites as the larger companies (other than Pisa), but starts later in the day (2), allowing you, if you're not so inclined, to avoid committing a full day in Tuscany, and giving you the morning in Florence. Includes dinner in Sienna.

We did a day trip through Viator to,Siena and San Gemignano. It was nice to not drive but we didn't have the time to to go into the Siena cathedral it was rushed while lots of free time in San Gemignano. I have done it on my own before and I think I prefer that as you have flexibility. Renting a car is not too,bad if you are comfortable with driving in other countries, you can easily see a few more towns that way and go at your own pace. We spent 9 days in Florence and still could have seen more there is so,much to,see and it is all so easily accessible. We did day trip to Venice on Italo train line and that was a big hit! I think with only 3 days you have to really think about if you want to spend half a day traveling around vs seeing sights in Florence.

Thank you all so much for your thoughts. I had not considered a joining a day tour; we have never done this. I suppose that there are some pros and cons. I like the idea of having the planning taken out of my hands, but then you risk things like not being able to go into the cathedral in Siena. Maryam, how did you find the tour that you took? Do you think that a teenager could tolerate it, and did you feel that they divided the time well between all of those spots in one day?

I did not feel rushed at all with our tour. We started out in Siena (saw the American cemetery on the way [granted just out the window] which was a bonus)! First stop was Siena: We had a brief introduction to the history of Siena on the Piazza del Campo (on the actual bus ride, a video was playing that explained things further, so it was nice that our time wasn't too wasted on there). Then, we headed up to the Siena Cathedral and entrance was covered as part of the tour. We were given maybe 20-minutes to walk around on our own in the cathedral. There was also time given to walk around actual Siena and we did some shopping. There would have been time to enter the town hall on the Campo, and maybe enough time to climb the tower if planned well. We had lots of time to walk around San Gimignano and Pisa as well. We had a pretty fun lunch at the farm/winery. All in all, it was a good option for us. Definitely can do on your own, but given that we were hoping to do all in one day, we went for it. Now, if I was planning several days in Tuscany, I would have just rented a car and done it myself.

Sorry, forgot about the teen question. There were other teenagers on our tour, and they looked okay. I thought things were just the right pace to keep it interesting. You have some nice free time. I guess it depends on the teenager, but the typical one would survive!

Thank you so much!

Jane - we just returned from Italy where we had 2 1/2 days to see Florence. We saw a lot. I'd be happy to send you my itinerary, if you'd like. You could use it as a starting point and add/omit.

I would stay flexible, not booking ahead for a car or tour, but planning to use the bus and train options for one or two daytrips, with Siena being the first one.