What to do when a child simply does not enjoy eating 3 square meals a day, but would rather eat snacks and drink his milk?
Just let him enjoy his snacks, but you have to watch out and get him snacks that are more nutritious then the normal cookie and milk snack.
If he prefers to drink his diet, you can try milk shakes in a variety of fruity flavours like banana and oranges. However, if he doesn't like the fibers in the blended drinks, you have to take an extra step and strain the drink before handing it over to him.
For the extra willful child, it's a matter of you being more stubborn then he, otherwise he will grow up to be more of a handful (not just in the manner of eating but in other things as well).
After all, a balanced diet is the best diet.