Aviation for Kids is a site dedicated to everybody interested in Aviation as well as Education, Science, Technology, and Parenting (my son is in most of the pictures and videos).
http://www.aviation-for-kids.com/
Since 1992, the EAA Young Eagles Program has dedicated itself to providing one free plane flight for any child who desires it. The Young Eagles is a national program with locations all over the country.
http://www.aviation-for-kids.com/
Aviation Activities for Kids has Four fun aviation activities for kids from How Stuff Works including rocket races and a stable airplane mobile.
http://lifestyle.howstuffworks.com/crafts/seasonal/summer/aviation-activities-for-kids.htm
Create your own flight plan and aeronautical charts with Skyvector. It’s a little tricky at first, but there are plenty of tutorials for budding pilots.
With Aviation Weather Center your can track weather conditions around the world.
http://www.aviationweather.gov/
The GeoFS website is a free, online flight simulator with visual imagery from around the world.
You can build your own plane with four amazing from-scratch aircraft, plans.
http://www.popularmechanics.com/flight/how-to/g631/4-amazing-diy-planes-and-how-to-build-your-own/
A fun game from the National Museums of Scotland. Build a plane and fly it during a rescue operation in the jungles of Borneo.
https://www.nms.ac.uk/explore-our-collections/games/plane-builder/
This British YouTube series, Amy's Aviation offers the basics of aeronautics. Suitable for children just beginning to explore the mechanics of flight.