It can get really hot in August so plan for that (sunscreen + sunhat & sunglasses for the kids at least, no kidding!) and if you're in the "south" (read south east) bring at least a bottle of water per person on day trips.
Paris can be wild with that small kids especially if you don't know your ways around, but it's definitely a place I'd recommend, but if so, plan ahead, you don't want to try to figure out what to do in the morning, if you don't like to wing things.
I'd avoid the south east, hot and not very tourist friendly. East is great, beautiful landsides in Nice and around. Bordeaux is beautiful and ypu can go to the wild ocean in an hour by car, or 2h to Dorfogne with its 1000 castles, cave paintings and more.
What do you usually like to do? Do you speak any French? Museums or the beach?
