Tough situation and tough questions you pose.
I suppose one way of thinking about telling your kids is this — if they are unaware that your friend’s father died by his own hand, then the topic of suicide may take some time to become one that has real personal and not just abstract meaning to them.
Better to form an opinion about suicide, mental health, gun availability, the interconnectedness of friends & family, and choosing between full and partial disclosure based on the situation.
While it IS true that the man seems to have died of a broken heart, that’s only SOME of the story.
Is the rest of the story important for you to share with them HERE and NOW?
Only you are in a place to know.
My best regards, and sympathies for your friend and his family.
e