Car rental for 6

Knowing the arrival and departure airports and how long you'll be in Italy would get you a better answer. The best you can get will be a seven-passenger van. You'd need all three rows of seats, which will leave you hardly any (no?) room for luggage. Two modest-sized sedans/hatchbacks will work much better.

It sounds as if you're in the starting phase of preparing for your trip. Your best bet would be to start your trip in Tuscany and take the train through Milan to Lake Como. Then take a train over to Turin. Many think that Tuscany (outside of Florence) is best seen by rental car, and I agree.
Flying open jaw into one city and out of another will serve your group better, as back tracking to your original entry point will be expensive and inefficient in time.

It sounds as if you're in the starting phase of preparing for your trip. Your best bet would be to start your trip in Tuscany and take the train through Milan to Lake Como. Then take a train over to Turin. Many think that Tuscany (outside of Florence) is best seen by rental car, and I agree.
Flying open jaw into one city and out of another will serve your group better, as back tracking to your original entry point will be expensive and inefficient in time.

You can get a vehicle which will seat 6 if you don't mind having no luggage and sitting squished up. And if you don't mind passing other vehicles in your big one on tiny lanes and tinier alleys. All drivers need an IDP and don't carry luggage on your laps - it can be deadly.

It might be cheaper to rent 2 separate economy cars rather than one passenger van. Check the prices but consider that you will have to incur twice as much gasoline expense and freeway tolls. Gasoline and tolls are not a big issue if you have a car in Tuscany only. Distances are limited, economy cars are fuel efficient, and in any case you won't be driving on toll freeways much. Having two cars has other advantages. First of all some ancient streets are very narrow and not easily negotiable by a large van. Second of all it will allow flexibility of travel with a big group. Maybe some of you may like doing something different a day, having two cars will allow to split the group and do different things. Regarding the direction of travel, I'm not sure where you are flying from/to. Como and Turin are relatively close in the North. Tuscany is 4 hours to the south of Como. An open jaw ticket with arrival in Milan and departure from Florence (or Pisa) might be best. In such case you would visit the north first (Lake Como + Turin) and Tuscany last. You will not need a car in Turin for sure. And a car is not that essential for Lake Como either. A train to Varenna will do and once there you can rely on boats/ferries/hydrofoils for the lake area. In Tuscany a car is not needed to visit Florence or any of the provincial capitals (Siena, Pisa, Arezzo etc.), however if you are staying in a villa somewhat out of town in the country, you will definitely need a car while you are there. A car is also very convenient to visit the Tuscan villages and the countryside.

I'm thinking the same as Ed and Roberto, two compact cars will probably get you around easier and cheaper than a big van. Remember to factor in luggage. Most cars/vans don't include extra room for every passenger's bags. Read about each vehicle carefully to make sure it will work. Every driver needs an IDP (international driver's permit) that can be picked up at any AAA office here, before your trip. Finally bring a GPS for each car (that you know how to use). You will be glad you have one - even if you never needed one anywhere else.

Thank you everyone. I really appreciate it...