Okay parents, this is for you - I'll try to summarize more of what I said in last Saturday's seminar on "How to Get Kids to Eat Vegetables".
Here's the problem with the word "vegetable": what usually comes to mind is something green and leafy, like broccoli. Now, there's no arguing that broccoli isn't a vegetable, it's just not the only picture we should have in our minds. An unpeeled potato is also a vegetable - with pretty much the same nutritional content. As with an orange, a bowl of popcorn, bean burrito or handful of pistachios. All these are "vegetables" in that they are botanically alike; they are all unprocessed plant foods, or "vegetation". Some are seeds, some contain seeds, and some are what sprout from seeds. Nutritionally, there's very little difference.
So instead of using the word "vegetable", let's just focus on getting our kids (and ourselves) to eat more unprocessed, plant-based foods. That would include all four of the following food groups: whole grains, legumes (nuts, seeds, beans, lentils and peas), fruit and vegetables.
To be thorough and convince you further, fruit and vegetables are exactly the same as far as nutrient content. Sure, many fruit have more sugars, but not all (avocados, tomatoes, squash, cucumber and zucchini are technically fruit by the way). Whole grains and legumes are only missing one nutrient: vitamin C, since they are dried by the time we eat them. But these are also the foods highest in fiber, protein and folic acid, so don't count them short.
What's important isn't if your children eat green vegetables, what's important is that the unprocessed plant foods are as high in nutrients as possible. And that can differ drastically, depending on the quality of soil it was grown on, where it was grown (in proximity to you), how in season the food is, and if it was vine or tree ripened. Organically grown foods are significantly higher in nutrients since the soil is replete in nutrients. Locally grown, seasonal produce lose fewer nutrients between harvest and our plates. And vine/tree ripened produce produce more nutrients (including antioxidants and phytochemicals) verses "conventionally grown" produce.
This is why I buy my produce from a CSA (Community Supported Agriculture - Google to find one near you), the Natural Foods Co-op, or Farmer's Markets. Sure, I pay more, but I'm investing in my child's immune system and lifelong health.