This may be too "black and white", but I see only two choices as I too have trouble with the concept of being paid for days I am not providing care (I do not charge for sick days-either on their end or mine-- and allow change in schedule up to a week in advance for which families do not have to pay for care they will not receive).
1. Plan to stay home on the days for which they have paid.
2. Have them pay in advance only for the days they will use (so on the weeks they only use two days they would only pay for two days).
Just my two cents
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