WE ARE SO CONFUSED!!! Travel in Italy

For the range of travel you're proposing, railpasses aren't needed. You can buy train tickets point-to-point.

As for the choice of car or train, it depends on whether you are staying in those other cities or doing day trips. Venice is too far for a day trip from Lucca so I assume you are planning a few nights there before going on to Nice. If so, I'd drop the cars in Florence after your stay in Lucca and rely on trains from there.

Be extremely cautious about driving a car in Florence. They have computerized cameras that will detect you in certain neighborhoods and historic areas where permits are required. You can search this site and see threads where people have received notices of very expensive tickets months after they were there. Take the train to Florence. It's really cheap from Lucca.

If you want to visit the Cinque Terre which is also nearby, again, take the train. With rare exceptions, tourist cars are not permitted in the towns and the parking lots above the towns are full during the tourist season.

While we are in Lucca, we hoped to spend just a day in Venice. We were expecting to take the train to Venice and come back in the same day.

Is this not realistic?

Lucca to Venice is going to be a minimum of 4.5 hours and then when you get to the station in Venice about another 1/2 hour to reach StMarks.
Not a day trip in my opinion.

For nine/ten people maybe a mini-bus is the way to go. It depends on which is of more importance to you, time or money. And of course there's the issue of getting everyone on board the bus within a reasonable time frame, agreeing on when and where to stop etc. Come to think of it, take the train. You can stay outside of Venice much cheaper than in the city itself but really you should plan on a two night layover so you have a full day in Venice. There's no way you can make this a day trip.

I live in Pisa and I've wandered around Florence in a car but not to go anywhere specific. Just like any big city, if you've not been before it can be confusing, and let's just say Italian drivers are not the most patient. I'd train from Lucca to Florence, or at least find out from the villa owners what's an outermost parking area in Florence where you can park the car and train in, in case you buy something huge. But, it will probably be 1-2 euros/hour for parking. Venice is definitely not a day trip, and if you try to make it one,you'll regret it. There's so much to see and do, I've been twice and haven't even hit all the main sites! I would plan on at least 2 days there, more if you want to leisurely walk around and savor the flavor, or if you want to go to Murano or Burano. Lucca's a beautiful city, make sure you spend some time there too!

The historic centre of Florence is very compact and easy to walk through and pass by lots of major sights within a few minutes. If you arrive in the Firenze SMN (Firenze Santa Maria Novella) Station, you can walk to the Duomo in about 10 or 12 minutes at a normal pace. As previous posters have mentioned, you'll probably encounter hassles if you drive (parking tickets in the centre/you'll need to park far away from the major sights). have a great trip!

Definitely do point-to-point tickets in Italy -- railpasses would cost much more than the individual tickets. Anything but the hill towns in Tuscany are readily available by train. I think Italy is one of the easiest countries for trains and connections. And, ditto, you should try to spend a whole day in Venice. (To save money we stayed in Padua and caught the 30-minute train to Venice and back for the day we spent there. Not only was the hotel much cheaper, but we also got a little time in Padua also--great town.)