I asked my wife's advise, as she knows the family and I dont and she thought they might be hesitant to sign a model release and not want their photos sold as stock. I ended up writing up a simple "release" for the mother to sign that gave me permission to use the photos for my website and advertising. I asked her to sign it when I gave her their photos and she was more than happy to sign. Also, she paid me twice what I was going to charge her so I dont feel so bad about not being able to sell the photos as stock.