I love the idea of helping children learn about creation through enganging them in hands-on, outdoor activities.
Here are a few books for when they get close to highschool level. They're more of the bookish sort.
All three books emphasize teaching students to learn a subject through the process of dialoguing or questioning. Polya's book deals with specific logical questions that help people to learn the math and sciences.
What Smart Students Know - Adam Robinson
How to Solve It: A New Aspect of Mathematical Method - George Polya
How To Study In College - Walter Pauk - An excellent book on learning and the importance of developing a strong volcabulary, but you will want pick through it yourself instead of giving it to your highschooler to read as it is interspersed w/ non-christian philosophy. The other two books are relatively neutral on that point.