Rate Questions

Whats a good weekly/hourly rate to watch 3 children overnight from 8:45pm to 7am? The children are age 11,6 and 3. The 3 year old is physically handicapped. He cant walk because he is partially paralyzed on one side. The older boys are upstairs by 8:30 pm so i would only be watching the 3 year old and putting him to bed. Maybe once a week i would have to feed them supper or give the 3yr old his medicine. Plus on occasion the parents would be working overtime sometimes 3 nights for 2 hours or 6 days. Im just trying to get an idea of what a fair wage would be? I live in Kentucky if that makes a difference. Im used to just watching one child at $10 an hour. Any advice?