I am a mother of three kids (5,4, and 2) so I can understand how kids have eating phases. I can truly sympathize with your situation. Don't worry, you will get through it. I'm sure.
I have learned that my kids have different preferences than I do and it's okay. Also they have eating phases, so one day they like something the next day they don't. It can be confusing, but hang in there.
Mu kids like a lot of frozen food. Especially at young ages when they are still teething. So I serve frozen waffles or pancakes, frozen tator tots, green beans, corn, peas, broccoli, etc.
I also make muffin mixes into pancakes rather than muffins, because it is less messy and still tastes good. I can also serve them without the syruo then, because the muffins have enough flavor an there own.
I serve veggies at breakfast because my kids are hungry enough to eat almost anything at breakfast and it sets the tone of the day to be healthier.
I serve hard boiled eggs, with or without the yolk. My girls like it with the yolk; my son likes it without.
Also: chicken nuggets, hot dogs (cut up small), Peanut Butter on bread, Peanut butter with carrots or apples, macaroni and cheese, shape noodles with parmesian cheese, etc.
I also try to reserve the fruits for the end of the meal. Once my kids taste fruit, they don't want to eat anything except fruit for the rest of the meal.
I also serve one thing at a time. I find that my kids are more likely to eat what is in front of them if they have no other option. Then I serve the next item. It means I leave the table more often, but they eat better.
I avoid adding things like salt, sugar, or even sauces. I find my kids don't need the added items and it saves on mess. But of course, if they see my plate having something their doesn't then I'm in trouble. My kids tend to think Mom's food is always better than their own. So I try to eat what I want them to eat.
When we do eat out, I tend to prefer buffet places. I like to let my kids try various foods without wasting money or ordering many different foods. And even though it is hard with a 2 year old, I like to let my kids pick their own foods from the salad bar. They tend to eat what they choose for themselves.
Well, this is getting long. And I could say more. But I will stop for now. I wish you the best of luck. You will do great. And if you get worried about balance, you can always get a multivitamin. But I'm sure your son will do great. Keep up the good work.