D.K.
Boy this is a tough one. I think I would want to proceed very slowly and establish a relationship with the mother of the other child first. I don't let my kids go hang out with anyone that I don't know very well and that includes family. I would want to know that the standards I have for my children would be respected. I'm pretty protective of my kids. I would have to be able to trust anyone that would be interring my children's lives. I agree that you should start with a public meeting. Maybe just have a play date with the girls at a public park. I would also move slow on the information I gave to my child and slowly work into the relationship details.