M.M.
Although my daughter has always been a great veggie eater, I have found that I can get her non-veggie eating friends and cousins to gobble up veggies by doing one simple thing.
While you are preparing dinner (or lunch), set a plate of carrots, brocolli, or celery, or whatever veggies you want the kid to eat (we usually like raw veggies) in front of the kid. They are likely starving, anticipating whatever you are about to serve them...and will munch on these while they are waiting. There was a time where I caught myself saying "stop eating all the vegetables, dinner is almost ready". Ha.