Adrenaline Junkie Theory Input Please

Can somebody please help me.  I do not understand the adrenaline junky theory, especially as it relates to child rearing.  What have I done wrong?  What have I, as a mother not provided for my children that they must seek this adrenaline rush (or whatever you want to call it, maybe it has a new name).  Case 1:

Ok, this is bouldering at Yosemite, maybe not so bad huh.

Well, what about this, hanging off the edge of Half Dome.

Not just content to summit Half Dome, after summiting Whitney the week before.

And you know, I can't nag too much about their adventures or they'll just quit telling me about them i.e. death defying night hikes, etc.
Please what concerns me is the universalness (sp? or is that even a word?) of this in all of my children, it's not just one child and even my only daughter is as much of an adrenaline junkie as her brothers, she probably has been the one that has inspired them the most. Brad (who was only 3 years old when Kerri left for college) asks all the time-"Mom, could Kerri do that?" This being said with great awe for the legendary talents of his sister.

So tell me, what does a mother do, just on Monday we were at a Labor Day party and people were commenting on Kyle and Brad barreling down a steep street on these little toys (mind you, they are now 12 and 14).  I could take away their toys but that would be quite a collection to stand guard over, skateboards, longboards, motorcycles, snowmobiles, skis, rock climbing gear, road bikes, skim boards, boogie boards etc.  Oh I suppose it is useless, even taking away all the toys they will do handstands on cliffs, and jump off the roof into/onto a pool, trampoline of whatever (that was Kyle and his friend Sam just the other night when the teachers had an activity, after everyone left they were jumping off the roof into the pool).

By now you might be thinking, she hasn't mentioned Bri, he must be the "sedater" one. NOT. Bri I won't tell the Jamison, Brittany, Focus story, but suffice it to say all the repairs the Focus needs are probably directly related to your leadfoot adventures.

Brent, longboarding down our street

Also note the lack of protection, yes hanging in our garage is a wall of helmets, you name it, we've got it, climbing, cycling, skateboard, ski/snowboard helmets, knee pads, elbow pads, safety glasses, you see I do attempt to be a good mom.   Note special sliding gloves (made from mom's cutting boards), hmmm you know your boys are up to something when you walk in the kitchen and see scraps of cutting board, you know those heavy white ones, the gloves are quite the creation.   Ok, so sometimes they do wear some protection.  Brent, I might also add that Kev says you owe him a longboard, whatever that is about, and Brad is sure that you are hiding his somewhere.  

Please children, share with me what your child-rearing philosophy will be.