South France is great place, but it can be quite hot in summer... Just know it in advance :)
Well, nice places to see there :
- Nice. A big city, quite international (also bit difficult to park the car), but very pleasant town center. Also quite "italian" in architecture, since it became French only in 1860. Nice seaside.
- Aix-en-Provence : 30mn by car from the sea, but very pleasant city with many bars, cafés, restaurants...
- Avignon : more inland city (I would say 90mn by car from sea), but pleasant place with the "Palais des Papes" dating back from centuries ago. There's a festival theater in summer bringing a lot of people and animation, it could be nice, but ask for the dates of the festival
- Carcassonne : again a bit inland city but impressive almost intact medieval town
- the Camargue area (between Marseille and Montpellier) : more nature oriented, more "wild", with many nice little places like Aigues-Mortes (with old medieval remparts). I'm not sure it's the place to go for a first visit in France... Maybe for a second time.
Biggest city is Marseille, with also a seaside... Some nice places of interest ("Notre Dame de la Garde", "Le Panier" which is an area looking like a little village, Cathédrale Saint-Victor with very old sarcofagos inside), but I'm not sure it's the best place to spend many days... If you want to go there, stay in Aix-en-Provence, and take a train to spend a day in Marseille.
Avoid Saint-Tropez... Way too crowded in summer and nothing special to see.
And it's true there are many nice little villages, not very known but who can deserve a visit. I'm thinking of Cotignac near Toulon which is quite beautiful. If you're into history, there are some remains here and there from Roman Empire and medieval monuments (the three abbeys of Thoronet, Sénanque and Silvacane for example).
Living in South of France :)