I've been taking a caravan to and through France for more years than I care to remember, but most of what I would suggest has already been covered.
Driving on the 'wrong' side can take a bit of getting used to and the French are some of the worst drivers in Europe according to their own statistics. Be particularly wary just after midday when they wil all be going for lunch. Many regard the inner lane on a roundabout as an overtaking lane and have no idea that you will inevitably take some of both lanes particularly on a small roundabout. Make sure your extension mirrors are set for the best possible view to your left and set the right hand side mirrors such that you can seen any kerbing on a corner - they are very fond of concrete and it would be easy to catch the side of the caravan or the mover.
I've used the site at Bec Helloin and agree it's good We tend to the smaller sites - farms etc. but another good one is the municipal at Doue la Fontaine - big aquadrome nearby, toglodyte village, Saumur, Chateau of Villandry etc.etc.
If you have a satnav set it up to give you speed limit warnings if yu can, but disable the 'safety camera' action as this is illegal in
Unfortunately Brittany and Normanday although very nice quite ofter share UK weather, so if you are really after the sun you may need to thin a little further south to be sure.
There have been several other threads on this topic in the last two years and it may be worth while looking back through them
Bon voyage !