$20+/hour, paid over the table, 2 weeks paid vacation (dates to be one of her choice and one of your choice), plus 6+ paid holidays and use of vehicle or reimburse mileage while working and transporting kids/running household errands

I am interviewing for a nanny job in a wealthy western suburb of Chicago. This is just for the summer. What should I charge per hour for 4 kids (nanny share)?