Lots of good things here so far!
One thing I would add would be that schools, while they usually teach some sort of nutrition.. do not spend enough time on it. And if the teacher is teaching the health part (as when I was teaching school), it is sent by the wayside if other academics need the time. Some teachers breezed through it because it was like taking a hard look at the way they themselves ate - not comfortable at all!
So as a parent, you cannot rely on the school to teach proper nutrition - or even to provide proper nutrition during meals (I remember another recent post at 3FC providing a school lunch menu that was ATROCIOUS).
You have to teach them how to make the right decisions, not just model for them. Teach them how to read food labels - it is a lifetime skill that is so necessary. Show them that there are healthy alternatives to things they like. For example, my soon to be 8 year old LOVES bologna and cheese sandwiches for lunch. So when I started my eating plan, everyone in the family started looking at the food labels & watching fat intake. At the grocery store, we compared his regular bologna, cheese, & bread for both fat & calories to low-fat bologna, cheese & whole grain bread. Then, he CHOSE the one he thought he should have. It was the right one, and it was his decision. He is very much like me - I hate people telling me what to do. Kids at this age hate that, too. So it has to be their decision.. we can guide them and show them, but they have to have the power to make the choice. He is very happy with his decision and now drives me crazy at the store checking all the labels for his favorite things. LOL! It is worth it, though.
The only way I can see helping your aunt's son, would be if your aunt would take an active role in modeling & teaching him. But that would meaning maybe learning a lot herself first - it would be worth it, but not easy. You can find good kids materials here:
http://www.mypyramid.gov/kids/ -- downloadable stuff in the classroom materials link, too
and here:
http://kidshealth.org/kid/stay_healt...d/pyramid.html
Hope this helps!