Stopovers in France - Ideas please!

[jobnockey]

Hi there, we're travelling down to the dordogne from calais in August in the campervan and planning a couple of stopovers. I'm just planning and can't decide where to stop!
My ideas so far are Chartres, Loches, Saumur or Langeais... we can do two of these, one on way there, one on way back. We preferably need to have a campsite within walking distance of the town to make life easier and these 4 places do have that option...
any thoughts on any of these to help me make my mind up??? We're happy enough wandering around interesting places but have a 5 yo with us so anything that appeals to him is a definite bonus...
any other suggestions of places I might not have thought of?
ps - the plan is to spend 2 nights in each place so that we can have a whole day in each town exploring.
Thanks!

A friend who drove pretty far south with kids last year raved about Le Mans, she had only heard of the race (as had I), but said it was gorgeous. No campsite recommendations I'm afraid, she was camping for the main part of the holiday but they stopped off in cheapo hotels.

We stayed at the Le Mans Castels site and weren't impressed so maybe don't stay there!! It was really noisy till wee small hours and the loos weren't very clean. More the guests not wiping floors in shower rooms and cleaning out sinks after doing the dishes dirty rather than actual filth!! Staff not interested in complaints (not just ours...Dutch family next to us complained too). Think they have lots of return guests who are happy to live like that so they don't need to please new guests!!
Ferme du Prunay is fab (near Blois) but its surrounded by sunflower fields so nowhere really to wander too!!)
Castels site near Angouleme is amazing but again its in the country.
Went down the east side last time and loved the Kawan site outside Troyes. Lac d'Orient. Fab if you fancy a slightly different route.
I've not really been a lot of help there...have I?!

Saumur is definitely a few days stop over.
It has a lovely chateau with lots to do in and the best zoo we have ever seen. I think it was called Bioparc and was so well laid out.

Troyes is nice

Thanks - i think we're leaning towards chartres and saumur at the moment but still time to change our minds yet!!!

forest view near chartres and the site at chenonceaux are both good, have a look at cool camping?