While it won't earn you any extra money you could ask for the first two and last two weeks of care to be paid now on signing making it clear that the money is non refundable should they not start care. I have also had some put a time in there that they can't leave care and use the money unless they stay in care the same number of months that you held the spot. ie if you are holding the spot for 4 months and they start in Sept but want to leave in 3 months they wouldn't get their 2 weeks back as it can only be applied to the last two weeks of care after 4 months. Then in Sept start charging them from the day they start so they are always paying two weeks in advance.

We are already getting into May and summer will be here before you know it. What if you compromised and made the start date August for the family. A lot of teachers need to be in the classroom for the last week anyways for meetings and to set up. That gaives the child time to get settled. Even if you offered a 3 day a week it works for both of you. You get some money, child gets to integrate and mom gets a few days to do all the things she didn't get done ready for the new school year. And means you are only 3 months without income which is still a lot but less than 4.