1. Ask your guests if there is anything you could have done to improve their stay. I do, and tiny things make a really big difference to perception of value as does personal communication, even just calling to say welcome and make sure they are settled in.
2. A guide book would be useful and interesting, local color etc.
3. travel times to various places "short distance" is relative, better in minutes etc. it might gall them to have to travel further than they had imagined.
4. You probably have done this, but if not look at other listings in your area especially those that have five stars for value and see if there is anything thay have that you could offer and what their decriptions and amenities are.
5. I stayed in a place once and their offer to stock some basics was a huge plus, we arrived late in the evening and all stores were closed. They left the receipt and we left the money. Or just have water, coffee, tea, a snack on hand - it's nice to arrive somewhere and have something to eat and drink.
Good luck, your places look amazing. I love that area of France!