Claire, you need to decide whether you're going to go 'autoroute' (and tolls) or N roads (toll free). You can use either viamichelin, or mappy.com to work out the distances, travelling times, etc., and then decide what's best for you. If you're having three days each side travelling, then I'd suggest sticking to N roads, and enjoy the travelling. Once you've worked out your route, divide it up into travelling days, and then highlight an area where you fancy stopping. Almost every French town has a municipal site, and at that time in August you should have no problems finding a pitch.
We use N roads, Calais, St Quentin, Soissons, Sezanne, Troyes (good municipal here), and stop at the municipal in Chatillon sur Seine, which is a good place to stop. The site's up on the hillside overlooking the town, and there's a nice walk into town through a woodland path. Lots of restaurants within walking distance. We've also stayed near Sisteron, at Le Hippocampe (not a municipal) and is a much bigger site, but great for an overnight stay.
Facebook
Twitter