I think the web pages need more color, and maybe a more "fun" font style. Good idea, just needs a little more tweeking.

I would add a "splash" page to the start page. It could be some sort of animated cartoon or humorous live action (i.e. person gets hit in head with ball, etc.). It would have been neat to use your group members in the instructional videos.

To make it more appealing to kids, I think there should be some sort of a splash page as your home page for the website. Furthermore, some instructions seems a bit wordy for kids, they are often impatient to read all the instructions.

I like the three sections: video, materials, instructions.

With the side column they made it very easy to understand how the website works.

The website can be made more good-looking if one of your team member knows the web design technique. I am not sure what kids like, the current simple design looks good to me.