I am almost 100% certain that neither Nissan model is sold in Italy. The closest thing to a Nissan Quest would be a Nissan Evalia, while the closest thing to a Nissan Pathfinder would be the Nissan X-Trail. I doubt either is carried by the major rental companies in Italy (Europcar, Hertz, Avis).
For 7 people you could get a Renault Grand Scenic which is automatic transmission, from Europcar. Or you could get a Ford Galaxy, also automatic, from Hertz. Both seat 7 people, including the driver. Europcar also carries the Fiat Scudo and the VW Caravelle, both of which seat 7 passengers. Google these models to see what they look like.
They have also larger vans (Fiat Ducato, Renault Traffic, Mercedes Vito), which seat 9 people, but those would severely impair your ability to negotiate the narrow ancient streets of Italian cities and towns.
Now, I must also tell you that renting a minivan costs as much as 3 economy cars, therefore, if you have at least 2 adults willing to drive there, you would save a lot by renting two Economy or even Compact cars, rather than one minivan. Obviously there would be no problems navigating in small spaces with those smaller vehicles. Economy cars tend to come with manual transmission only, compact may have both (you just have to request one with auto transmission).
For rentals over 3 days I generally use these consolidators:
www.autoeurope.com
www.kemwel.com
They are now part of the same corporate group, but prices vary, so check both. They both work with the major companies in Italy (Europcar, Hertz, Avis-Budget).
My uncle in Italy drove until the day he died at 92, so don't worry about being able to drive in Italy at the age of 69. Some rental companies place some restrictions/add'l fees for drivers over 70 or 75, but there are no restrictions for 69.