It works for me for a long time. Once after he read a story (or couple of sentence) for his dad (but not me) in the evening, I told him that his dad had a wonderful night, and he slept very well (he was smiling at the breakfast table). I asked my son does he know why daddy had a good night sleep. He told me he does not know. So I explained him that his reading has a magic, we sleep better and we are happier next day, because if we sleep through the night we are full of energy next day so we can play together. Since then he really thinks that his reading has a magic, so he ask me to let him read to us (even when is late). Sometimes we play that one of us already fell asleep when he is reading, so he can see the magic working. When he does not read to us for any reason, next morning we tell to each other how bad was the night we hardly sleep anything. When I tell him in the evening that is too late for reading, he is begging me to let him do it quickly.
Any other idea to share?