As some may know, I am learning American Sign Language. I found this great blog where there are 1001 Children's books translated into ASL. They are videos right on the site - they are well done and they choose wonderful books to sign.
I bet if your children are familiar with the book being signed, they'll be able to follow the story along.
A great activity would be to ask them to vocalize the story in their own words as it's being signed! It's great practice for communication skills, story telling, reading body language, following order/logical thinking etc.)