I agree with flying into one city and out of another to avoid back tracking. International flights out of Venice tend to be early. And transportation to the airport can be a challenge before 6am. That’s why flying into Venice and out of Rome would be easier.
For a first trip to Italy, Venice, Florence and Rome are typically the main highlights. But you really want to break down the days to see what you’re really dealing with. Two weeks including travel days go by fast. We (family of 4 with 2 teens) like to stay a minimum of three nights each place. Rome really needs a minimum of 4 nights, assuming no day trips to Pompei or elsewhere. That means:
Day 1: depart from home
Day 2: arrive Venice. Don’t plan much. Just check in to hotel/apartment and wander in the sun to fight off jet lag. Have a gelato. Or two.
Day 3-4: explore Venice
Day 5: train to Florence
Day 6-7: explore Florence
Day 8: Train to Rome
Day 9-13: explore Rome
Day 14: fly home
See how fast it goes! If you have to make your way back to the same airport you flew into, you lose a day.
Don’t under estimate the heat and it’s impact on the pace of your sightseeing. It could be brutal in Rome by early July. Get up early and get your main sights done early. Your kids will have the rest of summer to sleep in! We were in Venice in early July 2018 and the heat and humidity were taking its toll on lots of people in the afternoon. You could tell who was on a bus tour: they were all melting on the steps in the shade. We ALWAYS stay at places with AC in the summer, and it was sooooo nice to retreat to a cool apartment for a couple hours in the heat of the day. Then we went back out later in the day, refreshed and ready to explore. The summer nights in Italy are magical, and keep in mind that many restaurants don’t open for dinner until 7-8.
In Venice, we stayed at an apartment called Stella Marina rented through airBnB. We stayed in the red apartment (there are several apartments). Highly recommend it. The location is a quick vaporetto ride from St. Marks and we really enjoyed the peace (and AC!) away from the crowds.
