Also in your contract, include whether or not you require them to pay you while they’re on vacation. Also include whether you’ll require them to pay you while you’re on vacation. And give them a list of the days you’ll be closed (including the obvious holidays - Thanksgiving, Christmas Eve, Christmas, New Years Eve, New Years, Memorial Day, Fourth of July, Labor Day - b/c some parents would bring their children even if they thought you were open those days).
Just to give you an example. My mom started out her business being open 5 days per week, and parents didn’t have to pay when they were on vacation (they had to pay when she was on vacation). 15+ years later, she now is open 4 days per week and requires parents to pay 52 weeks per year and she now takes 4 weeks off per year (one in spring, one in summer and the two weeks at Christmas/New Years).