Wow, I just saw this thread and I’m shocked that the first option most people came up with is a drug (or even a natural pill)!
What about making sure that your son doesn’t have anything with caffine in it for a number of hours before bed time. This includes chocolate and coffee flavored products (like Coffee yougurt or icecream). There has been much said about food coloring contributing to this sort of problem also.
There is no reason to start giving children drugs or suplements before ruling out other problems- and even then only after consulting with your pediatrician!