A plan only helps if someone can find it. You don't need a family meeting. One trusted person is enough.
What they need to know
Where the binder is, and where the key is if it's locked
Roughly what's inside
Where any sealed envelope with passwords is
Who else knows
What to say
“If anything ever happens to me, everything you need is in the blue binder in the hall closet. The key's in my desk drawer.” That's the whole conversation.