Keeping your money safe

Hi we are going to Neptune Agde in South of France on 17th August for 3 weeks. This is our first time touring in France. My question is do campsites have safes that you can hire to keep your money safe, or do you have to keep it in the caravan ? Can anyone suggest somewhere safe in the van?. Also we plan to take table, chairs and sunbeds. Is it wise to leave outside of the van if you go out for the day?Thanks  Sue