Also Novotels offer really good family accommodation - pools, playgrounds, free breakfast for kids, children's menus etc. But they tend to be more motorway stop off points though some are in town. Website
We are booked in to the Novotel at Rouen Sud on our way back from Cognac to Brussels.
The Marais Poitevin region would make a good stopover. It's also known as the Venise Verte (Green Venice) because of its network of canals. www.marais-poitevin.com/?mode=recherche_par_carte While you're in La Rochelle, if you have kids, Futuroscope and Puy du Fou are also excellent days out. Hope you have a great time!