My mother’s philosophy was always “Dinner is at dinner time.” If you didnt like what was served, you ate it anyway because that was your chance. The kitchen closed after dinner.
My mother always told us that we might not love every meal, but it was food to keep us going. She tried not making things we hated, but you cant satisfy everyone!!
Another trick is to get your son involved in the meal process – come up with a 2 week meal plan that he helps plan out. So when he doesnt want to eat something, he was the one who helped pick it! (Obviously, a well balanced meal should be prepared)