Your local fire dept may be able to help you with the evacuation plan, or one of the other city/county agencies.
I think your plan would be individualized as to how many entrances there are, streets, etc... Up where you are, it would mainly be due to a fire wouldn't it? That is why I was thinking the fire dept may be of help.
As to the lost children...maybe letting the campers know to call you when they are found as well as if any are lost...