Tentative itinerary for first family visit to Italy

I suggest flying into Venice and out of Rome. Flights out of Venice tend to leave crazy early and the airport is not that easy to get to. Rome is worth three full day minimum (four nights) and another night is better. Four nights is a lot in Cinque Terre. Are you renting a car in Tuscany? End of August will be hot and a zoo with crowds of tourists in Italy, plan proactively how you will deal with this. Good to get out of big cities and visit smaller towns, but Cinque Terre will be especially crazy, I would think.

Unfortunately, our flights are already booked to fly into Rome so we can meet my parents for 3 nights. Maybe we should extend our Tuscany stay to 7 nights and only stay in Cinque Terre for 2?

Adding a night to Rome and one less in CT would not be the worst thing to do.

With your kids, having some play time days at the beach in Monterosso al Mare would be nice, so you could keep your itinerary as is, and be fine.

I agree about adding one to Rome and taking one from the CT

3 nights in Viareggio...what will you do? Lay on the beach? August will be very crowded with Italian vacationers. Do you know what an Italian beach is like in summer? That you have to pay to access it and rent a chair and umbrella? I would add two nights to Rome and one to Tuscany and skip Viareggio unless all you plan to do is lay on the beach.

We have a friend that said Viareggio was really beautiful and a must stay for a few nights. That said, he loves to lounge at the beach. After hearing how there is not much to do, I would rather add on a day in Rome or CT or Tuscany and do a day trip Viareggio.

European beaches--at least the sandy ones--tend to be massively crowded during July and August. It sometimes seems that half of northern Europe is soaking up sun along the Mediterranean. It may not be what you are expecting.