Hi there,
A couple of questions for your consideration:
a) have you driven in Italy before ?? cos they are manic drivers !! Have you checked if the train will do the job??
b) where are you intending to travel .. remember that a lot of the small towns in Europe have very small and narrow roads and you may be better off with 2 ( smaller ) cars rather than one large minivan. It might be less social but more practical.
c) always hire ahead of arrival ( I'm not saying pre-pay .. you can still pay in local ) as you will often not get your airline discount if you ask for walk in rates.