I mean, who doesn't like peas!!!!
Me!! And I am proud of it

I dont have this problem with my kids, but I do have it with DH. I started by pureeing the foods he doesnt like or chopping them very finely in the food processor and adding them to my cooking in a dish I knew he liked. Eventually I told him he had been eating broccolli and onion for months and to just eat it and then eat something nicer afterwards. His mum had always said if he didn't like something on his plate to leave it, whereas mine always said eat what you dont like first and then finish of with something you do like. DH now drowns his broccoli in sauce and eats it first.

If DS will eat a potato bake you could hide quite a few vegies in the sauce by finely chopping or pureeing them. Add a few more just on the plate so he sees them regularly, but not much, say a couple of pieces of carrot and broccolli, but most of his plate is the potato bake. You could even do finely chopped meats in there too if you have precooked them (chicken and pork will hide very easily in a white sauce).