In your Opinion - What's your most important use of time with Private Guides in Florence

In my opinion, for me the best use would be for the Uffizi and Bargello, for more personalized interpretation of pieces of art that interest me. I don't have kids and travel solo.

What do I think YOU should do with YOUR time? That's a totally different question, and that depends on your (collective) interests and preferences. I think that Uffizi is really the only thing that is so dense and overwhelming as to need a tour guide to help sort things out. I did not feel the lack of a tour guide in the Duomo museum, Pitti Palace, Palazzo Vecchio, or Oltrarno.

I like the idea of a general walk+ scavenger hunt for the kids, and the Ortrano walk.

Regarding the latter, I think the kids would glaze over pretty quickly at the Pitti; that one's room after room after room of stuff can be a challenge even for art geeks like me! The Boboli? Sprawling but short on flowers and can look sort of ratty during the dry summer months (BTW, what month is your trip?). The Bardini Gardens nearby often see more positive reviews:

https://www.visitflorence.com/florence-museums/bardini-gardens.html

During your Ortrano walk, for sure make the climb up to Piazzale Michelangelo and then further up to old and interesting San Miniato; the cemetery there has some engaging sculptures. Oh, and the author of "Pinocchio" is buried there.

https://www.visitflorence.com/florence-monuments/piazzale-michelangelo.html
https://www.visitflorence.com/florence-churches/san-miniato.html

Unless you do some splitting up, I think some of what you'll be able to comfortably do will be dictated by your littlest group members. For instance, I don't think I'd plan the belltower climb - with its 414 steps - for a very young child with very short legs, and I've already questioned the Pitti for younger kids in general.

Elsewhere in Florence, look at the family oriented programs at Palazzo Strozzi, the hands-on models at the Da Vinci museum, and children's tours/programs at Palazzo Vecchio (although all are for ages 4 or older.)

https://www.palazzostrozzi.org/en/edu/families/
https://www.mostredileonardo.com/en/leonardo-da-vinci-museum/
http://musefirenze.it/en/musei/museo-di-palazzo-vecchio/

I agree with Kathy-although our 6th grader loved a group tour of the Uffizi.

A 6th grader could probably handle the Uffizi - which the OP had decided against - and some of the Pitti. My own parents trotted us through art museums as upper elementary students. It's the littler folks, such as ages 3-7, I'm concerned about.

And apologies, Drew, for redundancy in regards to Palazzo Vecchio. I somehow skimmed right over that mention in your original post.

Kathy - Thanks so much for all the info.

As far as the ages of the children, they will be 3 (but a couple months away from 4), 7, 9, 9, 11, 12. So, other than me having to carry my 3 year old around some, the others should be able to handle themselves well. Our trip is in mid June, 14-21.

Good advice on Pitti and Boboli. We will focus elsewhere. I think the Oltrarno tour with some artisans and kids oriented craft/workshop stops sounds like the way to go.

I just can't shake that we will "miss out" on some context and info if we go see the David and the Duomo/Baptistry/etc without a guide to help bring it to life. Maybe we should do a couple extra hours..

Yes, we are already planning on doing the "Life at Court" in the Palazzo Vecchio, as well as a kids-oriented tour in the Galileo Museum. Da Vinci Museum was on my "maybe" list, but with it being so cheap and it looks like a quick stop, we will have to check it out. I had literally never heard of Palazzo Strozzi until your post - but I'll have to look into it now! Thanks!!