IME, the largest van available for rent in Europe without a special license holds 9. And that won't be big enough for 8 people with luggage. Moreover, it will be a massive hassle to maneuver it around small towns - and if you're only going to cities, you can't drive into them with it anyway without risking the enormous ZTL fines. And do you really want to be joined at the hip with the other family the whole time? I'd rent two cars.

Sorry, I can't recommend a hotel in Bologna, but I don't know how you could expect to find agriturismo accommodtions there. It's a city.

It might be helpful if you share your itinerary with us. It helps us to help you. We can lso more easily provide advice on the weather if we know where you are going.

A big van will be difficult to use driving through towns and in Bologna's medieval quarter.If you feel you need to have your own vehicles, rent two cars instead. Manual will be much cheaper than automatic and easier to obtain.Best idea is to take the train to Bologna from Venice. We drove to Bologna and happily left the car in a parking garage( 30E per day) the whole time we were there.Driving in the medieval quarter was challenging. We would have preferred to use the train but our itinery involoved driving before and after Bologna.
Since your trip is only a little over a week long, each child can be responsible for handling their own luggage on the train and carry it on the flights as well. We have traveled frequently with our famlly and those are the rules which have worked well.
If you want to rent a car/van or cars , look at www.autoeurope.com, a broker based in Maine.

Look at the Bologna Arts Hotels; they have several nice hotels in the city. We enjoyed our stay at the Novecento.But you won't want to have a car or cars.
Are you splitting the trip between Venice and Bologna? That is what I assumed.Both are wonderful destinations.

I'm in agreement with everyone about the cars. You won't be able to drive in Venice (just the outskirts), and you can take a train between the two cities.

My suggestion regarding a place to stay is to look at vrbo.com or homeaway.com. You can find accommodations that will fit all 8 people. We've used them in both cities and loved where we stayed. Flats are much larger than hotel rooms and give you all space and such. Check them out.

With a van, try the Aemelia in Bologna or one of the hotels near the train station. (Marriott, NH, there are others).

You can certainly drive to the periphery of Italy's cities and park your van. The size of your car isn't a factor about getting a ticket. Just don't drive where the signs say not to drive.

You will most likely see at least some rain in your time frame, and you could see downpours and winds. Real spring storms. Or it could be dry, but probably not for your entire trip.

This will give you some ideas of how to go about looking for the right-sized vehicle if you end up with an itinerary where you need a car:

http://www.frommers.com/community/forum.cfm/europe/italy/transportation-group-of-12-rome-florence

However, with 8 of you, there are vans in Italy that hold 9 plus have enough space inside to keep the luggage, presuming that for a 10 day trip you all do carryon (pack as you would pack if you were taking the train). You certainly get specific information about that. I have no idea if you can find one that has an automatic transmission. Maybe the Venice airport.

If you are just going to Venice and Bologna you don't need a car. Someone said "Just don't drive where the signs tell you not to" but it is not that simple. The signs are not necessarily easy to notice, and you can drive into a ZTL without realizing it. We did.

With regards to weather, we toured Italy in early April a few years ago and had beautiful weather in Rome (some of our students wore shorts, capris and needed sunscreen), and then ran into rain and much cooler weather in Florence and Venice. You will need to be prepared with rain gear even if you have a rental van.
I would also think the type of accommodations you choose will be based on what you are planning to do while in Italy. Are you going to be traveling as a large group all the time or do you plan to split up and possibly go to see or do different things depending on age and interest.

Thank you to everyone for your responses!

We plan on going from Venice to bologna, then to Rome. I would like to then drop off the car(s) in Rome or la spezia and try to take trains the rest of the way up into cinque Terre since we liked it so much the last time we went. From there we planned on taking the train(s) back in to Venice where we fly out from.

We wanted to have the car(s) from Venice to Rome because we wanted to explore as much as time allows in between the two.

We will be with the other family the entire time. Which will not be a problem. So, this is the reason we would like to be in one car. Also so we can take turns driving if needed.

Thank you all again for your help and knowledge.