Your kids go caching without an adult? Do they steal the car while you aren't looking? If kids are too young to drive, they aren't getting to the cache without an adult present. Surely that adult would be able to say, "Hmmm, this cache looks too dangerous, maybe we should try another instead." That's what the parent/adult is for, to make the informed decision. Its not anyone else's job to watch your kids. It's YOUR job.
If your kids are old enough to drive, then surely they have the sense to decide on caches. Or maybe the responsible/concerned parent would pre-approve caches for them, or even better, go along with them. Its a bonding experience, geocaching CAN be a family game. I have three teenagers at home myself. If I load them up in the car and say we're going geocaching, they grumble, but as soon as we start closing in on that first cache, they start getting excited and running to see who finds it first.
This is a technical game which takes a lot of thinking to pull off and find these caches. If you can do that, then you certainly have the brain power to figure out if a cache should be done, or walked away from. There aren't a whole lot of stupid cachers out there, running the GPSr's, PDAs, computers, etc... shows that...
BikerMike