What do you want their takeaway to be from telling them?
If they go “Yeah, so cool!” do you go “Yeah, I am” or talk about it as a regretful necessity as you did here?
If they’ll find out anyway, maybe let nature take its course and when they bring it up, you respond. You could do the “Let’s sit and have a talk”, but that’s where it really matters what you want their takeaway to be of it.
You’ve come to a Dad group to ask other dads.
What have you done to take care of yourself so far? You want to be in decent enough mental shape when the day comes that you tell them about this and that might take a while to work through this. It’s not a normal situation.