Hi again, jas!
Yep, I'll vote with the others that this is a really aggressive schedule with LOTS of moving around. Yep, every change of location eats more time than you think it will! You are also traveling with pre-teens (11 and 12 years old) who might not move at the speed you wish them to in the mornings? 😉
As I recall, you are flying into Rome and going directly to Naples on Day 1? So you only have 1 full day (Day 2) correct? That day is overly aggressive, and I'll stand by my previous vote to skip Vesuvius, and especially so if going on to Rome that evening.
Unless coming into Rome the night of Day 2, you only have 2.5 days for this one? I usually recommend 3.5 days/4 nights as the minimum to scratch the surface. That one takes some time to acclimate to/get your bearings. Unless you skip Siena, it looks like you can't add to that one if you MUST be in Florence on Day 8 but if you have 3 FULL days, it's workable.
Siena: What are your pre-teens going to do on Day 7? I've a feeling they won't be especially jazzed about a wine tour but you know your kids best!
Florence: you really MUST add time to this one if you can't skip it altogether. It will be busy and hot so worth slowing down to better enjoy. In a former post you mentioned that you, "...enjoy art but not hours of it"? The Uffizi is exactly that: hours of art. There's a LOT of great art in Firenze one can see in smaller bits/less time. I'm a personal fan of San Marco + some of the churches. A great half day is the climb up to San Miniato, see the church, explore the cemetery (the author of Pinocchio is buried in that one), take in the view from there and Piazzale Michelangelo below, and grab a seat at one of the cafes near the piazzale to rest the feet and enjoy a cool beverage, adult or otherwise. Anyway, you won't have time for the Accademia, Uffizi + duomo + walkabout with only a partial day. Additionally, will your in-laws be coming off an international flight that day?
Your young people might find Ospedale degli Innocenti interesting. Audioguide tours available in English:
https://www.museodeglinnocenti.it/en/visita-il-museo/
https://www.washingtonpost.com/lifestyle/travel/this-15th-century-orphanage-in-florence-is-now-a-kid-friendly-museum/2016/09/29/e063e3e2-8028-11e6-8327-f141a7beb626_story.html
https://www.tripadvisor.com/ShowUserReviews-g187895-d21330359-r576295825-Museo_degli_Innocenti-Florence_Tuscany.html
Pisa/CT: you know you'll have to stow your luggage somewhere before heading off to Piazza dei Miracoli, right? Hard to say what this year will look like but expect the CT to be positively heaving with tourists.
Lake Como: by the time you got there, you'd have little time for a partial day exploring the lake, I'd drop this one or add to it.
Short story long, I'd add at least a day to any location you've only allowed one night for, and another to one you've only allowed 2 nights for just to take a breath: more time for those young people explore the joys of gelato! One more note: as as many attractions, such as churches and museums, are not open every day, have you worked your schedule around those closing days?