One of the things I enjoyed about my childhood was the time I spent outdoors in the summer. The plants, animals, insects, and different ecosystems were just so fascinating. If you'd like to introduce your kids to these new worlds, you may want to start with free posters from Oklahoma Biological Survey and the University of Oklahoma.
They also have loads of educational resources, free pdf guides, and species info. Just browse around to discover how you can make nature an inspiring part of your child's summer memories.
Note: Free posters are folded and mailed. You can also order the posters in a tube if you pay the shipping.