PP. About teens liking San Gimignano. I was very interested in medieval history when I was in 8th grade. A lot of kids like "knights and princesses" material at some point in their childhood. What's interesting about San Gimignano is that it has more of these tall "medieval $ky$craper$" than other Tuscan places. They used to be common. Florence was full of such towers in the corresponding period. This kind of setup was somewhat unique to this area because of politics and landholding patterns.
Anyway, in a two hour or less bus tour visit, we only had enough time to buy gelato at a recommended shop and walk to a high point at ground level in town. I would have liked to go up in a tower and seen the town museum which has a scale model of what the town was like in the Middle Ages.
We took this bus tour out of Florence with a tween and a teen. In one day we went to Siena, lunch at a restaurant, San Gimignano and Pisa. It was efficient and made use of all the time we could spare. But a driving trip through Tuscany might be fun. There are castles there you can stay in.
In Florence, we stayed at a hotel in a medieval tower. However, the building was not easily detectable as such from the outside. It had a great rooftop view which my kids enjoyed. It's Hotel Torre Guelfa.
https://www.hoteltorreguelfa.com/
There's a medieval museum a few blocks away called Palazzo Davanzati if anyone wants more info on how people lived in the period of these towers. When we were there, a school group was going through it.
https://bargellomusei.it/en/museum/palazzo-davanzati/
Also in Florence, my kids liked the Leonardo DaVinci machine replica museum much better than the Uffizi.
https://www.museoleonardodavincifirenze.com/
The truth is, most kids are bored by endless landmark churches and art museums. So visit sparingly.