Yeah, I know. It's hard to figure out an emergency plan when you don't know a specific scenario.
But here are the basics. Everyone in your family needs to have memorized or on their possession an out of state contact. That way, when things have calmed down after a disaster such as Hurricane Katrina, even if the family gets separated, each person has the out of state phone number memorized. When they get to a phone eventually, they can call that person. Just think how many separated families in the Katrina disaster could have benefited by having an out of state contact!
Tip: Each family member memorize the phone number for an out-of-state contact. Practice this number at least weekly, writing it down and saying it (especially for the smaller children when possible).