K.E.
I will share an experience with you that I had with my now 16 year old, when he was younger, I could always tell when he was growing, you could not satisfy that child's appetite when he was growing, but when he was not experiencing a growing phase he would eat like a bird, and to this day, that is still the case. You could always try dressing up his food in fun ways if you are really that concerned about him eating, but if there are food that you know he likes, and has eaten before, just try things like funny shaped little meatloaves, or maybe put his mashed potatoes in a fun little shape on his plate, try dressing the food up so it looks more fun to eat. Hope this helps you some.