Hi Studentgirl,
As many have said, get a diesel manual. VW Golf is good for 2 w/luggage - you'd need next larger class for 3.

As others mentioned, GPS gives you the freedom to roam and get directions right to Points of Interest (POI). Without it, I think we still might be driving around Avignon looking for our hotel ;) If you decide to use GPS, I'd buy one and use it for a time before going on the trip to get used to the device while driving.

One somewhat confusing issue to watch for in new rotaries.
They may not be in the GPS database. If this happens just double check the route number you need to be on before you enter the "surprise rotary".

Enjoy your trip; Provence is truly beautiful.