To protect the kids from what?
I can't answer for the OP. But sigh... I would imagine things like this... if you realize you are poly AFTER kids come. It's always cleaner to sort it out and BE out to family and friends before kids arrive but that's not everyone's experience.
I've seen friends suffer the push-pull of warring family. They arrived at poly later in life. Some of my poly friends have relatives just IMPLODE at the news and then use the children as guilt trippage. As if the children do not have ears to hear grands or inlaws blasting away. It's rough on the couple, but prekids you could deal, break ties, etc and no little ears are being hurt or used in war.
Post kids? With relatives who megawigginz? It puts the child in the middle of their loved ones -- with kid brains that don't understand all -- "Do I believe mommy/daddy or grannies/grampies? Do I suck? Am I bad? Do people still love me?"
Just awful, and what did the kid do? Nothing. What did the parents do? Nothing but try to have more love in their lives. Terrible.