You've made good points. But how do we know she hadn't already stashed some belongings in another place prior to June 5? It's possible.
Maybe -- if inded this is the scenario -- this seemed like an opportune time, when everyone was focused on the funeral, etc., and not as much on the kids. Who knows?
I don't think it is possible that MK could tell a lie that could fool everyone involved for over three months. She heard a clear threat and saw what she believed to be a gun. For your idea to fly you must account for MK's part in it.