Pain de courgettes is delightful and generally a hit with children.

I’d want to keep things simple. You might need to finish up a load of leftovers at the end of your trip, and there is no easier meal for lots of people that lets you do this with almost anything than a Japanese curry.

When I’m in Spain for August I tend to do what I do at home in London but with Spanish ingredients and a Spanish twist and that’s make a series of vegetable side dishes/pickles with what I pick up at the central market. That way I can supplement ready made foods from local shops and take-home caterers, perfect when visitors come but it’s too hot to cook (I get these side dishes made up in the mornings). In France you should have lots of options, including the excellent Picard chain.

Examples of what I mean might be:
A pile of Julienned cucumbers with ribbons of sliced ham seasoned with a couple of tablespoons of soy sauce, a couple of tablespoons of vinegar, a teaspoon or two of sugar and a tablespoon of sesame (or olive) oil. Ideally sprinkled with toasted sesame seeds.

A couple of bunches of radishes, cleaned and sliced in half. Sprinkle with 2% of their weight in salt, let them sweat for half an hour. Rinse and drain and season with a drizzle of soy sauce, a little vinegar and some lemon zest.

Tomatoes chopped and tossed with herbs of your choice (I love them with mint when it is hot) and a little oil. Sprinkle with salt just before serving.

Coleslaw (although I can think of dozens of ways of using cabbage)

Basically “salades” with the original meaning: salted things.