Best way to get from FCO airport to Piazza Navona?

With that many people and that much luggage, the only thing that makes sense to me is either a regular cab or private car service.

The regular cab operation may be able to handle a party your size, but I'm not sure. If so, you might have a short wait until a vehicle that can accomodate your party is available. Perhaps someone who has arrived with a group that large can clarify. At any rate, only use the official taxi rank. Do not use anyone who approachses you in the terminal. The rate to your hotel will be a fixed rate, but not sure what it will be due to the size of your group.

A private car service will cost a bit more, but may well be worth it. We have used Rome Cabs a number of times and have also been pleased. It is a private car service despite the name. We just email them outlining our needs and get a reply in less than a day.

Perhaps a third alternative is having the hotel arrange for a transfer. The only downside to that is that you might get a regular cab, a car service, or the desk clerk's brother-in-law.

Even if you have to take 2 cabs, €110 for that likely works out cheaper or about the same as Leonardo Express + transport from Termini to Navona. Just make sure you get a taxi from the official stand.

I'd recommend a van service such as Car Airport Bus, which I used in May: https://www.carairportbus.com/
The company was very reliable and their rates were reasonable (about $16 per person).

The best way is simply two taxis. It is a fixed rate for up to four people and luggage. I think (someone will correct me) the fixed, day-time, rate is 45 E/taxi Just go to the starter outside the terminal. I know of no safety issue with public transit or especially taxis. What have you heard that concerns you?

55 euros fixed rate

Go to the official taxi rank out front
Hand the driver your address on a slip of paper and the 55 euros cash

Or confirm that their credit card machine is working and pay with card-they are required by law to accept cards

No tip necessary

Nothing unsafe about it

Just don’t be misled by anyone offering a taxi outside of the official taxi rank

Wow! I am amazed by how many quality replies I get in such a short time! Thank YOU ALL so much!
I just signed up for my first RS trip (2025 September to Greece ) and got access to this forum. Should have done it sooner!!
I will take your answers to my travel group for a quick vote:)

Welcome and glad you found us
But you don’t have to take a RS tour-this forum is open to anyone

Many here have never taken RS tours-including myself ;)

Some taxi are vans capable to take 7 passengers. Ask the taxi steward at the taxi stand in front of the terminal.

There are also limo services like www.romecabs.com which could provide that service for not much more than 2 taxicabs (I think he charges 150 euro for 7.