France in August in a Motorhome??

Hi, we've booked our first motorhome abroad for August this year and just wondered if anyone can give us tips for weather...i know it will be lovely weather, off to La Rochelle area, but with 3 young kids, and lots of items to pack, i don't really want to take duvets, as they will take up too much room, but will it be nice in the evenings??or too hot or anyone with any views?we normal do the air conditioned apartments in Spain, where we know what to expect...please help!!