If I understand you correctly, you have Sunday, Monday, Tuesday, and Wednesday, and two of those days are flight days. If that's the case, pick one base (Marseille, Arles, Avignon all work), and take day trips from there. You don't have time to go to Nice (3 hours from Marseille). In addition the the three cities I mentioned, without a car you can see Nimes (my favorite of all), Orange (the city is a bit grungy, but the Roman Theater with its intact theatrical wall is thrilling), the Pont de Garde, Aix en Provence. I know, because I had no car and (in 10 days) saw all of them except Pont de Garde (which, by all accounts, I have to return for).
While there are some smaller towns that have bus service, for lavender fields and wine tasting, you will probably need to take an organized tour - ask at your hotel. Trains and buses don't go to the rural areas so conveniently, particularly in the short time you have.
If you're using Rick Steves books, note that his Provence And The French Riviera book has MUCH more information on this area than his general France book.
Edit: cross posting with Laura - you see we said many of the same things.
