Here's the big idea: If children are allowed to turn foods down, they're not forced to eat, and they're given choices, they will come to choose good foods, know when they're hungry and when they're not, and actually learn to listen to their bodies and know what they need.
Change takes time. Don't send the bill. Don't "be nice" for two months and then say "I was nice and you weren't any nicer to me!" Be nice because being nice is better than not being nice. Do it for yourself and your children.
"Don't become emotionally invested in your child's choices. If you want to invest your emotions, invest them in creating an atmosphere where kids feel supported in trying what appeals to them AND turning down what doesn't."