please need feedback on itinerary

Are you renting a car in Puglia? It would be helpful for that region.
Amalfi Coast does not require a car. Neither does the Cinque Terre.
Big cities (Rome, Florence, Venice, Milan) do not require a car actually it's a hassle to have one there.
Tuscany (countryside and small towns) and Dolomites, are easier with a car.
If you rent a car try, to concentrate the places without a car at the beginning and the end of your trip.
As such I would do the Dolomites before Venice, if you have a car, and return the car in Venice. Then take a train to Milan.
You could also consider Lake Garda, instead of Lake Como. It's right there near the Dolomites.

Listen to Roberto! Concentrate your car needy days together at beginning or end of trip. My advice is 3 days are almost NEVER too much for any stop, because a half day is wasted every time you change locations. Check out of hotel, go to train station and travel, or drive, arrive at next hotel check in, etc.....this all takes time! So 3 days in CT, 3 days in Dolomites, 3 days etc, etc., gives you basically 2 full days at each location.

Unless you have a car in Tuscany, I'd base myself in Florence rather than Siena because there's more to see in that beautiful city.

As Roberto said, do NOT have a car in Venice, Florence or Rome, as the ZTL districts are many (traffic restricted to residents, and you WILL get a very expensive ticket, and believe me, you WILL pay it!.

Unless you're a hiker, and really need to hike Cinque Tere, I'd do what Roberto suggested and do dolomites / lake como. That's my opinion.

Any thoughts on Puglia area?
Also, from your suggestions, I should rent a car in Puglia and keep it until I get to Venice. Will car be a problem in CT area? Will driving be safe or crazy for an american? ;-)

Based on your interests, I'd suggest the Amalfi Coast over Puglia. Puglia is less-touristed, although Italians go there in droves for the beaches. Take a look at my trip report from last May. To me Puglia was about beautiful drives and great food. You could certainly spend beach time, but overall it was not an "active" vacation which is what we prefer. We were more active on the A.C. going to Pompeii, Ercolano, hiking near Amalfi Town.

Thank you all for your great feedback!! Based on all comments, I have booked airfare and accommodations.
Our trip looks as follow, God willing:
fly to Rome
4 nights in Rome
4 nights in Amalfi Coast
3 nights in CT (rent car when we are ready to leave)
6 nights in Tuscany
4 nights in Dolomites/ Lake Garda
3 nights in Venice (return car here)
2 nights in Milan
fly home

I enjoy the Dolomites and look forward to my return trip. Bolzano will be your gateway city to the Dolomites. You may wish to go to the Archaeological Museum and visit Otzi, the iceman. Your teens will be studying him in their history classes.

Buon Viaggio

Looks like a good plan Alma!

Julie, thanks for the tip, the boys might enjoy that. I looked at Bolzano, but decided to stay in Trenton just to be more accessible to Lake Garda.