Wildlife generally presents very little risk to humans as long as we use just a tiny bit of common sense. Most wildlife will flee any human at first sight. A few, like otters, are curious, but they won't get very close.
All you really need to tell the kids about snakes is to look before they step, and don't turn over tree branches, rocks, etc. If they see a snake, watch it and enjoy it...but don't tease it or try to pick it up.
During our EMS refresher last Fall, we had a presentation by the local fire rescue snake guys. They showed us a dozen or so snakebite pictures, and in every single picture the bite was on the fingers. I'm pretty sure there's a natural selection lesson in those pictures.
Snakes are very shy normally, and they will not chase you. Even if they did, you could out-WALK them -- they're a LOT slower than you are. Many water snakes, both venomous and non-venomous, will stand their ground, but they won't come after you...no matter how many silly stories you've heard.