Where do you want to start??? check out www.abc.com.au then the kids section
 for some ideas

Before you even begin to plan out how the site will look, you'll need to
identify the age group you will be targeting. In terms of design,
there's a huge difference between a site geared for children 0-7 and one
for 8-12.

In either case, a good start would be something like these:
http://newsletter.refinery.com/e_article000239865.cfm
http://deyalexander.com/resources/children.html

Hope that helps!

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Juvenall Wilson
http://www.juvenall.com
http://www.forumfox.com