M.B.
I have not read any of the other answers, but I had great luck with this.You have some really good ideas about not giving snack food in between. The only thing I would change because I know from being a mom to three and a teacher is you do not want to get in a power struggle with a child. You also do not want to make it unpleasant about food. It can cause eating issues later as in eating disorders.
I would put the food on the table and insist on pleasant meal times. My family always had a pleasant eating time together. Then if the child decides not to eat. Say "I am sorry (show real empathy not anger) you are not eating the good dinner". and take it away and throw it away. Either no snacks in between or fruit or raw vegies in between at regular snack times not right after they refused dinner. Then the next meal fix them a fresh plate of whatever we are having that meal. They will finally eat, but do not care if they do not eat everything or even try every thing on their plate. If you offer healthy food and make it pleasant and not a power struggle they will grow up eating a healthy range of foods. If they do not eat something, just matter of factly say "Oh I'm sorry you didn't try that it is yummy and eat some of it as you are throwing it away and say it's OK when you are big you will learn to love it". This piques their interest and makes them want to try it at some point. The main rule is to make meal times pleasant and not a struggle and to not offer sugary snacks in between where if they hold out on eating real food they get some bad substitute. You have good intuition about wanting them to eat healthy, but I would treak it to make it not a power struggle because in the end you will lose and they will grow up with resentment and an aversion to eating healthy which is the opposite of what you want.