Taking picture of foster kids?

My classes to become a foster mom don't start till July. I am sure they will go over this with us. But, I am just curious. I was told by a friend who's mom fostered, that they were not allowed to take pictures of their foster children. This was years ago that she told me. We are in CA and would be fostering through the county. I am a photographer and I would love to take pictures of them as they grow. It is especially important for the babies to have pictures of themselves when they are older. I definitely wouldn't post their pictures on anything. Another thing, are you allowed to tell (not post pics) your FB friends that you have a foster child?