hi mumof3beauties,
if his behaviour is caused by additives, it wont be just the morning food, but any food that he eats at any time of the day (results are not immediate, but may come a day or so after eating the food)
my brother was adhd, and his behaviour was food related. when my mother first heard about it, she put the whole family on an additive free diet, and his behaviour changed dramatically within about 3 days.(from impossible to normal)
you have to read every single label of every single food that your ds eats, including stuff like margerine that you may use in cooking. The simplest thing is to start from scratch and identify some additive free foods.
eg weetabix, milk, fruit, pure juice, home cooked meat and veg, pasta, rice etc, home made cakes or posh healthy ones from something like the Sainsbury's free from range but check the label! Or buy health food bars, but again, check the labels.
Also cut out foods with excessive sugar or sweeteners, and caffeine containing foods like chocolate, coca cola.
then try the resulting diet for about 3 weeks and see if you notice any difference.
there are quite a few self help books around, they describe fairly accurately the symptoms, and may give you more tips on exclusion diets.