All my son will eat for breakfast is pop tarts or frozen waffles with syrup ?

Try going to a health food store and buying organic waffles made with whole wheat. You can also buy Blue Agave nectar, which is as sweet as maple syrup only a lot healthier. You can do the same for pop tarts. At 4 years old, he will eat when he is hungry. Try giving him other foods and if he doesn't eat it, then put them in the fridge. When he says hes hungry again, try giving him the food again. Eventually he will cave in and eat, and if he doesn't then try going to a nutritionist.