Advice requested for sites that we should not miss in a 3 day car trip from Montpellier to Nice, including Pont du Gard, for 4 over 60 year olds.
A couple of years ago I based in Nimes and visited Avignon, Pont du Gard, Orange, Arles as daytrips. I don't know what a "not miss" is for you, for me it was Roman ruins and church history. Closer to Nice, I stopped at St-Paul de Vence to see the chapel.
Loved St Paul de Vence as well - just a great spot to wander around.
Another must-see in St. Paul de Vence is Fondation Maeght, if you like modern art. Two sights for nature lovers are the calanques and the Camargue. Nimes, Arles, and St. Remy de Provence are all great places to see.