How to block Angry Birds Toons movies in iOS App (like Angry Brids Go)
I was having the same problem.

This is a solution:
http://www.imore.com/how-block-specific-websites-being-accessed-safari-iphone-and-ipad

It was slightly different on the Air but very easy to figure out. I just checked "Specific Websites Only" and it was already populated with JUST kid friendly stuff that did not include the birds :)