My wife and I believe in teaching proper nutrition. However, we know how reluctant children are to listen to their parents when their parents are right (yet they always remember when parents are wrong). So, we have stumbled upon the Reverse Psychology method to teaching nutrition.
The plan is this: We give the children all sorts of junk to eat. Hamburgers, hot dogs, pizza, deep fried cheese and doughcicles, etc. for each meal. Then, we order healthy-ish, and let them "snack" on our "treats." Then, for snack time, instead of candy, chips, etc., we "let" the kids have a treat by giving them peas or green beans.
Children love anything they think is a treat, and they have a natural aversion to anything you put in front of them. I think we've stumbled onto a winner!
(note: the preceding was mostly untrue and recited for humor purposes, only. However, my children do enjoy snacking on frozen peas)