This is a bit of a tricky one to answer with any accuracy with the details you've given. Night hypos are bad enough in adults, and I can see why you've had 35 views and no answers

I don't want to be irresponsible enough to give specific advice on something that may result in an unpleasant night for you and your son and I guess I'm not alone.
What you give him is going to depend upon how low he is, what he's been doing and how much you would normally give him to raise his BG by a certain amount. Also, it's going to depend upon the insulin regime he is on (2 a day mixed, MDI etc) and what kind of insulin he takes. Also, when is his last meal / injection of the day.
If you post back with a few more details, you might get a few more bites. If you don't understand all of the above interactions 100% I personally would go back to the clinic and ask them for more details. Sorry if you think this isn't very helpful, but it really is a tricky one.
Gary