Do you think it might help if they would not read in their bed. They could read up until 9 when you go to bed and them go to sleep with no reading. I always like to finish my books and have hard time sleeping if I'm still in the middle of it. I used to read with a flash lamp under my bed when I was in elementary school. Still if I continue reading when DH turns of his light I have hard time of stopping and going to sleep. For me it helps if I only sleep in my bed and bedroom.