The Chart

This is an example of a chart that I made years ago. It has a different colour for each child on the top, and then colours for mom and dad on the bottom. (You can adapt this to your needs.) Each section has five minute increments, beginning with the bedtime and going backwards, which can be marked off.
The bottom of the chart is an illustration that shows that "obedience equals happiness and a correct bedtime" on the left; and that disobedience equals unhappiness and an early bedtime.



You may need to click on each photo to see clearly the illustrations, but you get the idea. And yes, my kids went to bed at 7:00 until they were in 6th grade.