You are not over reacting at all. I would not let my girls spend the night if I did not know (and I mean Know) the parents. So to let them stay at someones house that I didn't know then on top of that, the boys are staying. That is a definite NO. She will be mad, upset and angry and tell you, you are ruining her life. But when she has a daughter, she'll say Mom you were right. I love those moments. I am still getting them