Seven Kisses in a Row by Patricia MacLachlan

It's not fair, Emma thinks, for her parents to go away (for five whole days) and leave her with an aunt and uncle she hardly knows. What if they don't like children? But Aunt Evelyn and Uncle Eliot like Emma and her brother, Zachary, just fine. They also like rules. Rules about: Eating. Sleeping. Cleaning up. Messing up. Emma doesn't believe in rules. Not unless they're hers: Eating no broccoli, dead or alive. Sleeping: No sleeping in a room where night rumbles hide. Cleaning up: Don't. Messing up: Do. Emma can see that Aunt Evelyn and Uncle Elliot have a lot to learn about being parents. But that's okay---because Emma has five whole days in which to teach them.