If you have kids do a head count every so often to make sure you still have all of them with you. Children, especially little ones will do what is ingrained in the young of most mammals and try to hide from whatever the danger is. However illogical it may seem to us, small children may hide in a toy box, under a bed, in a closet, under a box, or behind a door during a house fire to name a few things. It isn't because they are trying to be bad, it is hardwiring of the brain of nearly all mammalian young; hide until the danger is gone.
If you have young children and you have the time to do so, take a moment and use a Sharpie pen and write: their name, your name, address, closest relative and their contact information on the child's torso, front and back. As horrible as it is to think about you may become separated from your child and a traumatized child may not speak to a stranger. Someone needs to know who they are and who their people are. If there is time, consider doing something of the same for yourself. I'm thinking natural disasters here, like flooding and what have you. Families get separated especially if something happens to the adult in charge.
Although we all teach our kids what we want them to do in case of emergency, most times what they remember flies right out of the window and is replaced with fear until the child is a little older, 10 or so. No matter that we say that we've drilled for such and such to happen and that they will do such and such, don't put all of your faith on it.
I'll give you a case in point. This happened to me when I was little, maybe 8 years old. Now growing up the way I had, I was a fair hand on the farm, could deal with most things that came along because that was just daily life, I didn't know any better. My family decided to take us to Six Flags amusement park as a treat that summer and I got separated from them. I wouldn't say anything to anyone that tried to help me, even though they were in uniform and it was their job. I froze, did the deer in the headlights thing that a lot of kids do. Took my parents 3 hours to find me and only found me by describing what I was wearing. The park attendant who had found me couldn't get me to budge, I stayed beside that damn bush the entire time. My parents didn't understand why I hadn't told them who I was and I couldn't answer them, just that I had to stay where I was.
Maybe I was just the freak kid on the block, but I don't think so. So yes, teach your kids what to do, do it often, but remember when the shit does go down, they may shut down and you'll have to be there to nudge them back into gear.
I dearly pray none of us ever have to deal with it, but I know that is a pray that won't be answered because we will have to deal with it. So do your head counts religiously. Head the group with an adult, tie a line to each wrist and end the line with an adult or the oldest child.