My understanding of temazepam is that it's a short acting med, ie makes you drowsy but doesn't help increase the time you sleep. Is ds having trouble falling asleep or staying asleep?
I had some success from cutting out caffeine and sugar and other stimulants from Kate afternoon on. One surprising culprit was Milo, so watch out for things like that in yr sons diet. A walk in sunlight in the afternoon can help the brain recognize the switch from light to dark. Cooling down the sleeping space (ie remove a blanket or use a lighter quilt) and reducing light sources esp pc and telly screens. I use an eye mask and always sleep heaps better with it on so that's worth a try too.