Practice Makes Perfect
Sitting everyone down and telling them the plan is good. Putting the plan into action and practicing it is even better.
I'm not suggesting you randomly start blowing your air horn in the middle of the night to make sure everyone exits the way they're supposed to. Here's why.
Once you've run through the drill a couple times, the people in your house are going to be accustomed to being woke up by false alarm air horn drills. They're going to be slower to react because they'll make the assumption it's just another drill. The more they hear it blown, the more accustomed to it they'll become.
Dad's testing us again, they'll think, as they drift off back into the deep slumber they were awakened from.
In a time-critical situation, this can be the difference between life and death.
There's one way around this and that's to plan drills in advance. Let everyone know before they go to bed that there's going to be a drill that night. This will eliminate the element of surprise, but will still result in a pretty good run through of the mechanics of getting out of the house. Instead of using the air horns, go door to door and knock on the door until the person in the room wakes up and enacts the plan.
Make sure everyone knows there will be no unplanned drills, so if they wake up in the middle of the night to the sound of an air horn, it's because there's an emergency situation.
When you practice, you need to work on the following types of drills:
Drills where you grab the bug out bags and go.
Drills where the bags have to be left behind.
Drills where you have to use alternate exits.
Second-story exit drills.
Window exit drills.