Announcement issues. PLEASE READ

Okay my fiancé and I are having some difficulties deciding together whether or not to tell our families were pregnant this weekend. First problem is his sister just bought a house and gets the keys the day after my fiancé wants to announce. In my opinion I think it's stealing her thunder.. thoughts?? AND I'll only be 4 weeks along! We want he love and support from our family but I'm nervous because I've already have a miscarriage. What are your ladies thoughts??