My SO told his kids we're expecting....

Jennifer • Hopelessly in love with my soulmate, mother of four beautiful kiddos: 💕03/03/08, 💙05/06/10, 👼💙09/28/18 - 06/02/2020, 💙03/27/2022 and current expecting #5 in July

My SO and I had planned to wait to tell his kids that we were expecting because I didn't want it to cause problems with their mother. She's absolutely crazy and who knows what she will do with this information 🤷 Anyway he decided to tell them last night, they are both excited which is nice and he asked them not to tell their mom yet. As a mother I know that absolutely they are going to tell her. I suggested he tell her today while they were at school before they get a chance. He chose not to. Is it so bad that she hears it from them? I mean obviously his kids are a part of our family and she's not so it makes sense we would tell our family first. I read in a psychology journal that when a divorce happens and one partner moves on and eventually has kids with someone else, even though the marriage is done and neither party wants it back, having a child with someone else creates a sort of finality for the other person in a stressful way. She's already a loose cannon so I'm a little worried to say the least. The kicker here is she left him so it doesn't make sense most of the time when she acts crazy. It's not like he left her for me or anything, he actually tried pretty hard for a while to get his family back for the kids sake even though it was a toxic relationship. We are so happy together and so excited for this baby, but I know that this will cause even more problems with her moving forward. The cat is out of the bag now so all I can do is wait and hope for the best 🙏🤞Have any of you gone through this, on either side of the coin and have any insight or suggestions? ❤️