My wife and I stayed on camping Mondial in Vallon Pont d'Arc. Site is on river with direct access, close to local town, five miles from Pont d'Arc. Very clean facilities, nice restaurant and takeaway which were still open in late September and good size swimming pool. We booked holiday through Select Sites in Abergavenny so benefitted from savings on ferry and the site takes Tour as You Please vouchers in off season so you win all ways.
There are lots of sites near Mondial so you can take your pick at the time of year you are going.
The winding roads on the high cliffs of the Ardeche are spectacular but don't venture along them with the caravan!!
Hope you enjoy your holiday.
Ian