airport transportaion question

With 4 people, a taxi is likely your best solution. The Camilia is walking distance from Termini station, but unless you pack real light, it is likely a bit of a slog. The Leonardo Express train will cost you 42 EUR for the 4 of you. A taxi is 48 EUR fixed price, so the extra 6 EUR for door to door service would be worth it.

Same with Venice. The bus to Piazzale Roma is 8 EUR per person and I don't think there is any reduction for children that age, so that is 32 EUR. A taxi should run about 35 EUR. The Santa Chiara is right there, an easy walk from the bus stop. There is also a taxi stand right there. Kind of a toss up, that one.

Here is a google street view photo of the Santa Chiara. Rotate to the left and you will see the yellow articulated bus that goes to/from the airport, and taxis. I see the green taxi building is advertising 40 EUR ride to the airport.
https://www.google.com/maps/@45.4381445,12.3194755,3a,60y,352.77h,88.43t/data=!3m6!1e1!3m4!1sFQcudHHYl_JZUZIUqUwQ5g!2e0!7i13312!8i6656

Since you arrive at 9 PM--you do mean in the evening and not the morning--take either a taxi or pre-arranged car service.

Taxi. cabs are your friends

yes we will get to Rome 9PM.

Is there a way to purchase cab, or car service in advance?

Paying more you could book a private driver that will be waiting for you even if the flight is delayed. It's a nice and easy way to arrive in central Rome, but There is no need to; there are always cabs queuing in front of airports and train stations in Europe.

In Rome ignore drivers approaching you at the arrivals: they are licensed, but they can't look for customers inside airports and ask more than 48 €.

The fixed fare is 48 € 24/7, baggage included. There is no legal reason to ask for more, including strikes, rain, time of the day and the Pope's death. If a driver tries to make more money, just take a pic of the license and call the hotel staff. Same if the credit card machine mysteriously stops working. It's a driver's problem, not customers'.

No one expects you to tip taxi drivers (and waiters, maids etc. etc.)

Piazzale Roma is the only ugly area of Venice, where you can still see and hear wheeled vehicles. It's a parking lot. I stayed there because of budget, but I knew what I was going to get. Do you?

Thank you for the feedback about Taxi

No I did not know anything about hotel neighborhood :(

This is the hotel but it is non refundable:

https://www.tripadvisor.com/Hotel_Review-s1-g187870-d229024-Reviews-Santa_Chiara_Hotel-Venice_Veneto.html

On the positive side, if you are arriving in Venice by train the Piazzale Roma is close by. We have stayed in the area around the station and walked/used vaporettos to see the other parts of Venice -- don't worry about your location.

It’s not a bad area and the hotel is right on the grand canal next to the Constitution bridge, a pedestrian bridge designed by Santiago Calatrava, the world renown Spanish architect.

However it’s the place in Venice where cruise ships, road tranportation, railway (the station is across the bridge) and city water transportation (vaporetti) all meet on the Grand Canal, so it’s a very very busy spot where hundreds of thousands of tourists arrive and go at all hours of the day and night.

The hotel however gets good reviews and looks really nice, obviously it is logistically very convenient for tranportation in and out of Venice. My only concern would be the possibility of noise, also at night, given the foot traffic and the huge crowds necessarily congregating there on arrival and departure to/from the city by car/bus.

For good measure, carry earplugs in your luggage and ask for a room facing the water, at least you’ll avoid the cars/buses noise, if not the foot traffic and the vaporetti.

We always use romashuttle.com for transportation to Roma from FCO and the cost is about the same as using a taxi. They meet you just outside of the frosted doors at Customs. They hold a sign with your name as you exit into the meeting area and provide door-to-door service..

Buon viaggio,

The hotel however gets good reviews and looks really nice, obviously
it is logistically very convenient for tranportation in and out of
Venice.

I was going to say the same, Roberto. Reviews are very positive, including comments about convenience of location so I wouldn't fret about this choice.

Since you asked for the best way, consider a private car service. After a long flight, jet lag, not being familiar with the area, there is nothing better than having a private driver meet you inside the terminal and whisk you and the family to your hotel. No fending off the privateer cabs, waiting in the regular taxi line, lugging bags on a train, or just having a "lost" feeling. We can not say enough good things about Rome Cabs. It is a private car service (not a cab company) but only cost a little more than a regular taxi. For four people it probably wont be that much more than the train. We always use them and have always been very pleased. Go to romecabs.com and see what you think. We usually send an email and they answer us with a quote within 24 hours. You do (or did) have to pay cash (Euros) at the end of the journey but not in advance. Seems to me that they now take credit cards, but since we always pay with cash I'm not sure about that.