Tuscany part Itinerary

We need to know your transport preferences to offer suggestions. If you are driving to Lake Como, you would not want the car in Monterosso so you've have to pick up a new rental.
I'd probably lose my mind in Lucca with two littles. Maybe an agritusimo with a pool (which might still be open in late September, not sure)? Country mouse or city mouse is what we need to know!

Lucca and Sienna are great, but I would go with Sienna.

@valadelphia, was planning to drive all the way. I was planning to live the car parked during my time in Monterosso anywhere and only use it to move between places. Would it be better to return the car and get a new one?

@geovagriffith, would you just do Sienna? and maybe a side trip to Lucca on the way?

Maybe check with your accommodation in Monterosso? I know there are some tiny lots, in summer for sure I'd say you are going to have to park in La Spezia in a garage. So, just not sure though I know it could be complicated.

Yes, how you plan to travel will make a big difference. If you have to see CT, I'd cut it shorter and give the time to Lake Como. There's not a lot to see and it will be hard with young ones in two.

Remember 3 nights is equal to two days. I suggest you sit down and do a detailed itinerary, including travel time from one location to another. To me that's a lot of moving around with a family even with the amount of time you have.

I also suggest considering staying in an agriturismo in Tuscany, but only if you have a car that will allow you to explore the countryside.

@valadelphia, don't yet have an accomodation, wonder how far in advance is good to reserve, was planning to do end of the month. I wouldn't mind parking somewhere and taking a taxi or train to it.

@DougMac I made a points reservation with Gran Victoria Hotel (excited!) for 3 nights. I can look at extending in a different hotel. You feel there are more things in Lake Como compared to Cinque Terre? I'll look into an agrotourism, any recommendations?

I have not been to the lakes.
In CT, there is a small beach at Monterosso but kids are too young for the hiking there (steep, drop-offs, carrying the one year old while watching the five-year-old would not be fun). I'd look at somewhere like Sestri Levant (have not been here just hear it recommend for families with kids often) or Camogli/Santa Margarita Ligure area. There is more room to spread out there, maybe take some ferry rides, ride the cable car in Rapallo. Even some of the hikes in Portofino park could be done with the older child. (If you take transport up to San Rocco, you can gain access to a flat-ish path across toward Portofino). Hotels in both will offer parking whereas in CT it is precious.

I will definitely need to look into this. Thank you!