How to tell my MIL

So, my brother in law and his fiancé are also expecting, due in late November. It’s the first grandbaby for my in-laws, so everyone is very excited. I want to tell them all soon but I don’t want to pull focus from my very pregnant sister in law. Plus, I can’t do anything cute and subtle because MIL will think I’m just referring to the already pregnant girl 😂 and they all live together right now so they’re all gonna find out at the same time...any thoughts or suggestions? This is a total surprise pregnancy, just got our BFP last night! Due May/June 2019.