We are flying in and out of Nice at the end of September. Please comment: 3 nights in Nice (Hotel Royal or another with ocean view); visit Monaco, Villefrance sur Mer via train visit Vence (by train?) pick up car, drive to Avignon, stopping in Aix on the way; stay 2-3 nights, tour Pont du Gard, St Remy... drive to coast (stop in Arles) to Hyres, St Maxime, Frejus or Antibes? prior to returning to Nice to fly home. Hotel ideas, missing any "not to miss: towns?
Which town is best for the last two nights on the sea?
I recommend that you include the Luberon in your itinerary if you like perched villages and pretty scenery. Cassis is one of the most picturesque places in France. The drive along the coast from Cassis to St. Tropez and on to Cannes is mostly very scenic apart from the big port city of Toulon. Cannes isn't far from the Nice airport. Hotel Renoir there is a small gem located within walking distance of the old port; parking can be reserved in advance.
I would recommend driving part of the loop route that Rick's Provence book recommends and stopping at Seguret, a lovely walled village, and doing some wine tastings in Gigondas or Vacqueyras if you enjoy wine. The Gigondas cooperative in the central square will give you an easy introduction to several different red wines to taste. Les Baux is a must see, very spectacular cliff-side fortification very close to St Remy. (Honestly, St Remy is not really all that noteworthy unless you are there on market day. I recently spent five nights there as a base of operations in Provence, but it isn't really a must-see place on its own except perhaps for its Roman ruins. But you can see better Roman ruins in Arles or Nimes on the way out from the Pont du Gard.) I'm not a fan of Aix as compared with Avignon; there's a lot more to see in Avignon. You might want to pick a convenient place to stay in Provence to use as a base so that you aren't pulling up stakes daily. We like the Hotel Amandiere in the outskirts of St Remy; it has free off street parking, which is well worth considering. Have you thought about a night in Marseille on the way back? I know that Rick isn't a huge fan, but the Vieux Port and Notre Dame de la Garde are worth a half day stop, and you can find lots of reasonably priced hotels within a five minute walk of the port. The Hotel St Ferreol is a good choice; clean, well-appointed, with an excellent breakfast included. I'd recommend that you pick up the RS Provence guidebook and spend some time with it; putting together an itinerary is the trickiest part of trip-planning, and the most subjective.