Unfortunately, most of the accumulated info on bugging in and out with kids was lost when ETS changed whatever they changed.
Do you live in the flood plain? That's simple to fix: GET OUT. I live near Centralia/Chehalis. We were mostly marooned, but we didn't flood. My worst problem was when the wind blew up the chicken's plastic flap and wet down a good two quarts of layer pellets. And no, I didn't mention that to the people who lost everything. I bought with disaster in mind.
As was said above, your main two issues are bugging in and bugging out, in that order. Bugging out on foot with kids is really not an issue, esp with them the age you have. If things deteriorate to that point, you are in deep trouble.
I would make a list of what you need for each age group now. The chances are excellent that you will need some form of what you've got now. Then think about each facet under no-power, no-heat, no-help conditions.
Start with what is likely to be most important. Not being a mother, my first thoughts are diapers, food, diapers, warmth, diapers, medications, and diapers.
How many diapers do you use per week? Do you use the disposable kind? What do you intend to do when (not if) you run out? I would keep some cloth diapers and a bunch of liners on hand. PNW... rainwater collection to wash them.
Heat is important to small bodies. Be able to shut down the rest of the house and live in one or two rooms to conserve heat. Open house plan? You'd better make plans.
Baby food can be created with adult food and a knife and fork: mince and mash.
Sick baby under disaster conditions? Pedialyte and baby meds. Talk to your pediatrician -- you must be on a first-name basis by now! Tell him/her what your intentions are. Ask if there is such a thing as a breathable hood for babies/children to protect them from ash fall.
Check out the Red Cross sites: http://www.redcross.org/services/disaster/0,1082,0_581_,00.html
Check out your local government disaster sites: Here's one for King County:
http://www.metrokc.gov/prepare/Emergency shelters tend to provide space (not much), cots, food and water. That's it. You're mostly on your own for the rest.
If I read the tanker correctly last week, the railroad was shipping at least one tanker of sodium perchlorate to the NORTH. WTF??? Combine that with a derailment. Or a leaking tank (train, truck, you choose) of chlorine? You'll have to be ready to run immediately. What do you take? Which direction should you go? Got a NOAA radio? Got gas in the car/truck?
Always keep in mind that disasters of any kind tend to strike at the worst possible time: at night, when it's snowing or raining, when there isn't much gas in the car, etc.
Also, type up a Babysitter Handbook. Keep it pinned to the wall near the phone in PLAIN SIGHT, and sit down and go over it with each and every babysitter. I am reminded of a 12-year-old babysitter who smelled smoke but couldn't find the source. She called 911 immediately, then she gathered up the three small children and ran with them across the street to a neighbor where she saw a light on. A short time later, the house was engulfed in fire. Could your babysitters do that well?
Blast's Handbook was mentioned above. It's WONDERFUL!
And check out those smoke alarms designed with children mind. Instead of the whoop-whoop that sleeping children can't hear (a scientific fact), they have Mom's voice recorded: "Get up! Get up! Go out the front door!" over and over.
You can do this! Look, I have my four CHICKENS trained to run into a cat carrier when I call them and toss some grain inside. If I can train a chicken, you can do this!
Sue (still working on the cats...)