Large amounts of insulin are required to bring the blood sugar down
. And when the DP weakens, all the insulin-on-board causes a rapid drop in blood sugar
levels. You have commented on this. And your are right. It is a pain!
The sensible way to handle this, is to reduce breakfast carbs. Instead of feeding him cereal, give your son eggs, cheese, sausages etc for breakfast. His blood sugars won't go so high, you won't have to use so much insulin, and the late morning lows should ease off.