Parenting Dilemma

One of the things I have serious trouble with as a parent is watching my children do standard childhood things that are actually very dangerous. We have a rock climbing "wall" as part of their playset, as well as a fairly steep ladder that goes up to the slide, and each time I watch Jake climb either one my heart leaps into my throat and I have visions of him falling. We also have these huge rocks on our property and Hannah has just recently discovered how fun they are to climb. Watching her scamper over them makes me want to throw up. She is allowed to climb them by herself (although an adult has to be outside with her) and Jake is only allowed to climb them with an adult by his side. One part of me wants to say "get down off there...you are never climbing those rocks/wall/ladder again" but deep down I know that doing those things are how they learn to be confident, strong adults and not scared, nervous wrecks. Besides, what kind of childhood is it if all they do is sit inside and/or stay on the ground. I tell myself "What's the worst that can happen? They'll fall, get a few scratches, maybe break a bone but all that stuff can be fixed and then they've learned a lesson". Of course then my mind starts to wander and I think of all the ways they can fall in just a certain way and end up paralyzed or dead. What I've decided is that it's just easier not to watch. You send them out into the big, bad world and hope that all your "be carefuls" and "make sure you pay attention to what you're doing" has sunk into their conscience. I would rather not watch it happen so I go outside with them, sit with my back to it (peeking over my shoulder every now and then), and sit there cringing while I wait to hear a scream and a thump. Of course, my preference is to send Lincoln out with them and let him deal with it.