Could you make your son lay down too as an example to the others with the idea he will rest a bit and then let him get back up. I used to let Jennifer do that sometimes when her and Melissa shared a room. She laid on her bed till her sister fell asleep and then could come out. So her job was to see that her sister got to sleep. A lot of the time she herself fell asleep for 20 minutes or so too which was great because some days she needed it but didn't want it.