I was going to recommend this same site. http://corneredcat.com/Kids/firstlesson.aspx is really the best, most sensible, most effective take on gun safety for children that I've come across.
The extremely excellent site, Cornered Cat, which is designed by a mother of five exclusively for women who own guns and/or want to know how to teach their children gun safety, has some great information about kids and guns. I highly recommend that all mamas read it, even if you never plan to own or handle a gun yourself. Not teaching your children the basic rules of gun safety just because you yourself do not own guns, seems to me to be as shortsighted as not teaching them to swim just because you don't own a pool or go to the beach. Guns are everywhere and knowing to
Stop! Don't Touch! Leave the Area! Tell an Adult!
could literally save a child's life.