I am a type 1 diabetic, and I notice that even cereals such as plain Cheerios digest very quickly, causing a brief spike in sugar until the insulin catches up with it. In my case, I can avoid this by injecting my insulin a little bit before breakfast to give the insulin a head start unless my waking blood sugar is too low to allow for this. Another option would be to add some fat or protein to slow down the digestion time of the cereal. Fats in particular will slow down digestion times.
The carb and protein combination at bedtime sound ideal. Again, the idea is to have him eat something that will digest slowly. Nuts are good as proteins, and they also contain fats that slow down digestion. Healthy fats, at that.