You're free to display pictures of anyone on your website if you own the copyright to those pictures or if the copyright owner has given you consent (either specifically or by clearly placing the images into the public domain).
The copyright owner is normally the person who took the photograph. A parent or guardian has no specific rights in regard to the publication of images of their children. (For example I could legally take pictures of children in the street and put them on the internet. The children's parents would have no legal right to demand that I removed the pictures as I would hold the copyright in them).
So the issue here is not one of parenthood, but of copyright. If your daughter holds that copyright then she can legally demand that you remove them. But if someone else took the pictures then only that person can demand that you do so.
Chris