Here’s your chance to build a 2-week itinerary

How much time do you intend to spend in Venice and Rome? Knowing exactly how much time you have for Tuscany and coast would help.
I'd forget Sardinia, but there are great beaches in southern Liguria and southern Tuscany.
2021?!? and I thought I was an obsessive planner!

Need to know which month too--there is a bog difference between June and August.

I think I would do Isle of Elba for thé coast bit.
A question : why don’t you want to visit Florence?

When do you arrive in Venice, and when do you depart from Rome?

Travis, I planned our Italy trip around RS South of Italy tour, four days prior in Rome and five days afterwards in Calabria and Venice. The people on the forum were very helpful when I needed to narrow down specifics. I asked a lot of silly questions since I hadn't traveled in years. But I did a lot of homework on my own. I started planning almost a year in advance. The trip went together great and we had a wonderful time.

Based on your thread title, it sounds like you want the people on the forum to plan your trip for you. Why don't you buy a guide book to narrow down what you want to see and do. Use Google search to find more information. Read old forum threads since many of your questions have probably already been answered. Rome2Rio is one source for transportation options. Booking.com and TripAdvisor will help narrow down hotel options. When you figure the basics out, I'm sure people will be very happy to help you tweak your itinerary and answer questions.

It’s in June.

Is your trip in 2020? How did you book flights for 2021?

It’s 2020. That was a typo.

It is always hard to design a trip for others; sometimes hard enough for just ourselves. Anyway.

So, twelve nights. Think about this:
Arrive in Venice, stay four nights.
Train to Cinque Terre, stay two nights.
Train to Siena, stay three nights.
Train to Rome, stay three nights.

If you more nights, add them to Rome.
Venice. It’s a great place to get over your jet lag, and fun to explore. Your older children would enjoy the night life in Campo Margerita, where the student population of Venice hang out of an evening eating pizza bought by the slice and drinking spritzes. Many will think I am crazy, but just ignore the big ticket attractions, the DK Eyewitness Top Ten. We have found in Venice that it is the “off Broadway” things that we most remember, the small details. Get hold of a copy of Secret Venice by Jonglez, maybe in your library, but otherwise it is worth buying. It lists many of the small things, details that you would otherwise miss.

Maybe do a boat tour with Gian-Luca, which we did half a dozen years ago. Link is here. https://www.likeavenetian.com/driving-a-boat/ The tour is really worth doing, particularly with a child.

Train to Cinque Terre takes about five hours, so if you make an early start from Venice, you still have a decent chunk of the day there. We visited the CT, spending two nights there; for us that is sufficient to get a handle on the landscape and the way agriculture works there, terraced olive groves and so on. We stayed in Riomaggiore (I think, in any case the closest town to La Spezia, the most southern town). On our first afternoon, we took a ferry ride up the coast to Manarola and returned on the local train. Next day we trained to Vernazza, walked to Corniglia and trained back to Riomaggiore. A child would find the walking hard going, and not that much fun. If looking for a beachside holiday, I would not pick the CT, although Manarola does have a beach.

Train to Siena from CT is about three hours, maybe train to Florence and bus to Siena. You could hire a car at Siena for maybe just one day, and take a trip into the country, or maybe just take a bus to a small town for lunch. Remember that parking in just about any Italian town is somewhere between a nightmare and a horror movie.

So a day looking around Siena, and a day in the countryside.

Train or bus from Siena to Rome, about three hours, for your last three nights.

How critical is Tuscany vs coastal/beach time? You mentioned wanting to avoid crowds, and you’ve got Venice and Rome locked in for busy places. You could drift off the usual cow path and head south from Venice along the Adriatic instead of heading to Cinque Terre (which is short on beaches), get some beach time, check out some cool towns in Le Marche such as Urbino and Ascoli Piceno. Then cross the Apennines via Umbria or Abruzzo back to Rome. This is well off the beaten path as well as a decent fit with your criteria - but misses Tuscany and CT completely.

The only tricky part is transportation decisions. The train options will be primarily regional, not high speed. A car is more flexible, and the driving is not hard, but there will be a lot of it. There are bus options too. My choice would be train down the coast and pick up a car when you turn inland.

This break-from-the-herd suggestion requires more work to find your own desired route, but could be a great adventure and a unique memory. You would have 2 of the 3 usual first timer destinations, and one all your own.

Something really important for Venice.
You need an actual paper map. Phone navigation just does not cut it in Venice, where a main street might be only a metre wide.

Why spend your valuable time in Europe going to the beach? Forget about Sardinia. You only have two weeks.

There are lots of picturesque places in Europe. If you haven't been to Venice, it will knock your socks off.

Two weeks in Italy, I would recommend Venice, Florence and Rome, with a side trip to Siena from Florence.

As Joe's now deleted post said you asked for help in 2017 and you also have a concurrent thread about traveling with kids. Have you been planning for the past two years what you want to do and where you want to go? You've booked your flights so you've started the process. If you don't want to plan your trip ask your wife to plan or enlist the help of your older kids. Get everyone involved so all can enjoy your trip. When you have nailed down what you think will be a doable itinerary, ask the opinion of the forum. People will be glad to suggest alternatives if needed and answer questions you may have.

I love the planning stage. I'm already thinking about which of two trips I want to do in 2021. Planning is learning -- about the country, customs, major and minor sites to see, trying to learn a few phrases in the local language. I spend a lot of time and energy learning what will make my trip great and what will also accommodate my traveling companion. I don't have the time, desire or experience to plan someone else's tour. It is not rude for posters to tell you use a reputable travel agent. Travel agents are paid to put together tours especially if there are logistic questions.

Hi Travis, Aussie has laid out a very nice plan for you. I'll offer another idea that is very similar. I only offer it because you mention that you are struggling, and perhaps it will help you think about "how to" plan your itinerary. It's how I sometimes start my trip planning, although things usually veer off in fun and unexpected directions after I do more research.

I will sometimes start by looking at several tour itineraries and find one (or a few that I can combine) to approximate what I'm thinking/ For example, this "Italy in 13 Days" tour matches your flight plan and is very similar to what Aussie has drawn up:
https://www.ricksteves.com/tours/italy/my-way-Italy

I can't be as efficient in my sightseeing as a professional guide. And I like to have time to "wander" without an itinerary. So I'll often double the number of days in a locale. You might:

• skip Florence and swap Siena instead, as Aussie has suggested.
• add a day here or take out a day there, or add/drop a city, according to the overall length of your trip and your interests

Once you have a sketch, you do have to research the transport to see if that 1/2 day allocation is sufficient for a given transfer, or if you need more time, possibly adjusting the overall itinerary.

Sorry, if this is a painfully obvious process, but since you mentioned you are struggling ….it might give you a framework.

A few suggestions from my reflections on planning a trip for next May (which I still have not finalized!)

Crowds and world class sites go together so you will have to decide the relative importance of each. I assume you want to see Venice since you are flying in there. I am planning on going there next year and the advice I plan to follow is to stay in Venice proper so you have mornings and evenings without crowds. I would stay 4 nights.

Then consider whether you want to mix in some less visited sites as a way to avoid some of the crowds. We plan to go to Verona for example.

I also am leaning towards exploring Umbria hill towns instead of Tuscany since it is less crowded. Perhaps that would suit you as well.

I don't know the coast of Italy very well but my experience is that it is rocky and very well developed. We spent a day on the beach in Positano a couple years ago. It was pleasant enough but only because we were exhausted from too many days of strenuous hiking. Otherwise, it would not have been my preferred activity in Italy.