A plan that has never been tried is a document. Trying it once turns it into knowledge, and once is enough.
The whole exercise takes twenty minutes. Say where the meeting points are and have everybody repeat them. Pick up the bags and see whether they can actually be carried. Walk to the near meeting point. Ring the out-of-area contact and tell them they are the out-of-area contact.
You will find two or three real problems, every time. The bag is too heavy. The torch batteries are dead. Nobody knows the number. The child thought the meeting point was somewhere else. Finding them now costs an afternoon.
Then put it down. Preparedness is not a hobby and living in a state of alarm helps nobody. Once a year, on a date you already remember, check the bags, rotate the water, talk it through, and go back to ordinary life.
That is the whole thing. A household that has done this once is substantially safer than one that has not, and no further anxiety is required.