I would NOT require reading. That turns a great fun activity into a chore. Encourage reading by all means, but don't require it.
Hoagies has links to websites on all subjects for kids. Take whatever precautions you normally would on the web, but we have found some great sites.
http://www.hoagiesgifted.org/links.htm
If you want something more structured, the Core knowledge series by E. D. Hirsch, offers a broad general survey of educational topics.
Does your child read? Does your child have any specific interests?