How do you announce a pregnancy to grandparents-to-be who absolutely cannot stand your SO?

I should probably add to this post by saying that our parents have not been able to stand us together for 8 1/2 years (9 years in November.) My mom and his mom are mainly the issues. Stepparents and bio dads are meh about us. There are technically 8 grandparents.

•His mom: Hates me.

•His Stepdad: Doesn’t care for me.

•His Dad & Step Mom: tolerant. Understand what its like to have the world against their relationship.

•My mom: Hates him.

•Moms BF: barley knows bf, but supportive.

•My Stepdad (Married my Mom): Deceased (May 2012, but loved me and only wanted what made me happy, had some resentment towards my SO.

My Bio Dad: Deceased (March 2015), •Loved me endlessly and wanted whatever made me happiest. Met my SO once when we were early teens- no bias.

Families: I’m the youngest of 6, and my SO is the oldest of his. - For my family this will be the 4th grandchild. This will be the first in his family. I’m certain all the grandparents will want to participate, but I just don’t want the toxicity from our past influencing how they treat our little Tigger (nickname until the sex is revealed.) I want everyone to be a part, but I understand if anyone wants to be rude or ugly, then that is their choice and they are actively choosing not to be a part of their grandchild’s life so that is entirely on them.

So I’m entirely frustrated this is gonna go up in flames.