CA - if your kids are in fact young, then as I said, shield away. I'm with you that preteens have no need to be given a talk about porn, but realize that you should probably talk to them sooner rather than later. My parents NEVER gave me a talk about it other than a passing remark about it being degrading to women, which I took as crap because it's a job that you do because you want to, but that's off topic.
I agree with you that kids need to be shielded to a point, but we're kids, we are curious little bastards, and we will find a way to discover things and get ourselves into trouble despite your and anyone else's best efforts to prevent it. The trick is to realize when your kid is progressing from innocent childhood curiosity into young adulthood, and to know when to stop shielding them so much so that they can handle new things in a mature way. Obviously that's very easy for me to say, but nearly impossible to do exactly right, but I hope you get my point about there coming a time where you have to talk to your kids about adult things, be it porn or cigs or whatever, before they discover them for themselves and regard whatever things you say about them as crap. Kids believe their parents if the parents are the first people they hear something from, but once your kid discovers porn or cigs for himself, its extremely unlikely that he will take your word about it over his friends word, because his friends have just as much influence on his opinions as you do, provided he gets in his opinion first.
Again, my 16 year old opinion, so maybe I got that completely wrong, but thats my thoughts on it, and I'm only a few years out of the transition from being a little kid to a young adult, so I'd like to think I have a basic understanding of what its like:]