OP in August it gets very, very hot - so hot down in the South that activities are very hard to even contemplate let alone get on with. Last summer was an exception, but usually we get 40 degrees plus for 4 months with barely a thunderstorm to break the heat up. And we are just North of the Dordogne. Further South can be brutal.
Many French consider the lakes and rivers instead of the coast due to the warmer water and flock to the Big Rivers for their own holidays, they hire canoes up river, take packed lunches and games and activities, stop regularly for ice creams and trips to the odd chateau on the way, and drop the canoes off at the end - the roads are full of canoes being taken back up river all summer long.
Pretty much most large towns and cities are interesting with loads of history. I am in a rural village and yet can see a 12 C church [which still rings the bells every 30 mins], out of my window here. They didn't have a Henry VIII knocking them all down!
Most cities will have decent posh hotels and restaurants, things going on, and there are a plethora of camping type options if that floats your boat. There is almost too much choice.
There are also water parks, lakes with activites going on all summer long, with lakeside bars and restaurants. You can pretty much throw a dart at anywhere in France and I guarantee you'd be able to find some water activities, a decent hotel, a restaurant, a historic town or village, forests, walks, cycling trails, church, chateau within 90 mins drive. Don't discount the Chateaux, the history is pretty brutal and every one is fascinating.