I owned a pre school years back., age 2 thru K. Had 75 kids. Trying healthy foods didn't work. What works is pork and beans and weiners, macaroni and cheese, spaghetti etc. Once a month, brought in Mc Dog food happy meals, I called them crappy meals but kids eat that stuff. Carrot sticks or celery sticks ok for snacks. I know some of those kids who are adults now. They look pretty healthy to me. Full stomachs are always better than healthy foods that end up in the trash can and kids with empty stomachs.
LOL.....my daughter went to a great local pre-school for 2 years- they had a cook on staff- and they served the kids relatively healthy meals- vegetables or fruit with each lunch- and the kids did eat healthier.
It gets harder when kids get older.
You make it seem like we should make no effort at all to provide healthy food to our kids. There is a middle ground where more healthy food is available and kids get enough to eat.
Of course if we just load up the food with enough salt and sugar- they will eat it- and we end up where we are today with teen obesity rates soaring.