There are certainly many here who can assist, without question, however, for a site (sorry Manny) SPECIFICALLY for the parents of children I'd also recommend www.childrenwithdiabetes.com as well. By definition that is their focus...
It is NOT that he cannot eat various foods in the LONG term, its always a quest of BARTER, and awareness. At one point he could eat the cereal AND the BOX it came in, without problem, NOW he must be aware of the quantity(ies) and FOR THE MOMENT, stick to SINGLE servings rather than gorging, the way he, his friends once might have done.
The reason is he NEEDS to be aware what a single serving consists of. Not 1.5, not two, not five servings of something.... ONE single serving. Once he can do that without much trouble, THEN, he can in time return to a less restricted approach. But until then, he cannot pretend...
The idea is to make an iron clad HABIT, then, then give us more flexibility. The restriction is temporary, in most respects. Some foods he will NOT be able to eat, without paying a serious price for (ie injected units of insulin to prevent the sugar spike), others he can simple barter/trade for as a choice. Such that at the end of the day, when he adds up everything he's eaten, he does not go over a certain number of calories/carbs, eats enough vegetables, proteins, etc..
A C.D.E. dietitian will be helpful getting that squared away. But the "restriction" idea is so he can learn what single servings are about.
There are a whole bunch of things you can substitute and neither he nor anybody else in the family will ever be the wiser. Breads, what's he like? Other foods he REALLY misses? As a general rule, things are going to be rough... he is likely in the honeymoon phase, where for a short-time things are still kinda working, not entirely broken yet.
In time... the honeymoon will be over and the injections, etc. will no longer be kinda "optional", but absolutely required.
So lets start at the beginning, what are your worst problems, biggest fears?