Should children be more concerned with what they eat so that they don’t have health problems when they get older?

In a perfect world, children could make and should make the best choices possible. In reality, it's really up to the parents to set a good example and provide them with the correct choices. If you grow up with the correct choices being made then you are more likely to eat the same foods out of habit when you grow up. Of course there will be times to overindulge and treat yourself, but if you have a good foundation to begin with.....it's a good start.

Given a broad range of types of foods available to them, toddlers (12-36 months) tend to choose naturally to eat a good diet.

Kids need guidance and good modeling by parents on eating properly

That makes it easier for them to eat properly as they grow.

Since children are usually depenant on adults to feed them, I think the responsibility should be on us to teach and for them to learn propeerly.

I'm not sure we should make eating properly a "project" for childen, but rather make it something very easy to incorporate into their lives.

Yes.