I like your idea of covering the stairs while the family is locked in the bedroom. When I lived with my parents, in a large 3 story, that was my Dad's and my strategy. It was difficult to get everybody in one room quickly but Dad and I would meet at the top of the second story staircase and cover it while everyone else was safe in their own rooms. Had to do it twice, both false alarms, but we were verey quick and I beleive would have been very effective.
"Suppose you were an idiot, and suppose you were a member of Congress, but I repeat myself." Mark Twain