I would change your contract as well. I dont charge parents for when I am closed. But they must pay for their time off. If you are worried about the mother pulling her kids (loosing/replacing 2 kids can be a burden on you), I would negotiate with her. Perhaps she would find it reasonable to pay half a months fee each, and pay you for their time at the cottage. She should be somewhat reasonable considering how long you have had her children, and obviously she wants to continue care if she is talking about next year already. I wouldnt want to loose 2 kids, so I would be willing to find a common ground with her! Good Luck, do what feels right to you because you are the boss