We just came back from 9 nights in St. Remy/Luberon/Cassis.
Cassis-- Beautiful, everything starts in the town harbor. Get a hotel there, such as the Cassitel or the Golfe There are lots of good seafood restaurants with catch of the day and view of sailboats. There is a well-maintained city beach, but the best connection to the Mediterranean is that the Calanques national park is adjacent to the town. Port Miou and Port Pin are within a one-hour walk from village centre, and not overly strenuous. Calanque d'en Vau is another 45 minutes and a challenging hike, but the destination is rewarding--look it up. We were in Cassis two nights. We drove to town from the Luberon, but parked in a paid lot and walked everywhere we needed to go. Parking is scarce, but available early and late in the day. The good thing is that if you are in the harbor, everything is very close. Cassis is busy, but not overcrowded or overpriced like other coastal villages, and they don't have the Calanques.
St. Remy--This is a perfect-sized Provencal town to be busy enough without being crowded or difficult to navigate. It is very walkable with a nice busieness district, good restaurants and points of interest. There are placards in places where Van Gogh painted some of his masterpices while a patient in town. The town is also a great central location for day trips to Nimes, Pont du Gard, Avignon, Arles, Chateauneuf du Papes and Cotes du Rhone wine regions.
One other place you should visit if not stay is L'isle sur la Sorgue. The canals that flow from a divided Sorgue river flow make this a unique, picturesque town, The Sunday morning market is one of a kind.
Hopefully this is hepful,
Happy Travels,
Matt