My daughter’s first mom found us on facebook. Now what?

My daughters birth mom found us on facebook and contacted us a month ago. We corresponded and everything is great. We decided it was best to tell our daughter about her. Well one thing led to another and now we are going to meet her and my daughters biological sister tomorrow. I am very excited but don’t know how to set boundries. It is just moving so darn fast. Any comments or advice would be more than welcome.