Okay, so it sounds like company-wide announcement first and then start getting into the 1:1s quickly to prevent people from suffering in purgatory.
Being let go is definitely not personal for anyone, it's not a cheeky excuse to let go the low performers. I'd keep them all if I could, I've got good references for everyone, we got phenomenally lucky with hiring - just not phenomenally lucky with everything else.
I've worked at places where I can't do things like: give realistic interview feedback, give proper references to people leaving; I hated it. Now that I'm in a leadership position - as badly as it has turned out - I can at least make my choice to do these basic humane things.