Just got back from an enjoyable week I'm France.
Was going to mention the cost of the tolls, but you aren't travelling far so that shouldn't be an issue.
We found a lot of the carparks were free, which was a nice surprise. Also, many attractions weren't too expensive (approx. 20-25 euros for four) although maybe we were lucky. The wine tasting tour was under 10euro, including the tasting, so we all enjoyed that!
The supermarkets aren't too expensive. We took cereal from us, and bought baguettes and cheese for lunch. Bbq in the evening,
I second others who have said to basically raid your home cupboards for pasta, beans, cereals, condiments, etc or go to aldi or tesco and buy the cheapest, value, and smallest packs you can find.
bon voyage!