Those who enjoy the comprehensive nature of the Sports Illustrated Kids site will also enjoy the Yahoo! Kids Sports site.
Though it doesn't have as much actual information as the Sports Illustrated site, there are more games and fun elements for kids just starting to get into sports. One daily feature is a sports themed joke. There's also an Ask Earl feature that includes multiple sports questions.
However, sports themed games are really the stars of this site, so it's perfect for a kid is perhaps still more into playing sports than they are into following them.