I sympathize completely. Unfortunately, aside from the very basic "safe mode" (which only filters out what Google considers legally inappropriate) there are no real controls for parents.
A few years ago it was actually easier, because we could keep the computers together in a communal area (my home office) and actively monitor what the kids were doing. Of course, it meant they could monitor what their parents were doing as well, which kept everyone on the level.
Now that my kids are older and their computers are in their rooms, it is much more complicated. The fact that they are now in their early teens is irrelevant to the content. They are still minors and still very impressionable. (I won't go into the details but take my word for it, they are not emotionally ready to handle more mature themes).
When I was a kid my parents didn't have to worry about any of this stuff. The Internet wasn't around as we know it and, although this type of content existed, it was not in your face and was certainly not available at the click of a mouse, even to adults. If you wanted to find it, you had to go looking for it, if you knew where to look.
Now it's all over the place, in plain view, and its a parent's nightmare. This happened in one generation and those of us who grew up without it are not only trying to figure out how to protect our children, we're trying to figure out how control and cope with it ourselves.
My daughter is an extremely talented artist and her computer is equipped with a drawing tablet, scanner and a lot of software tools to help her build her portfolio. You see some of her simple work with pixels here in these forums in a couple of animated smileys. She creates all the artwork for my son's gaming web site, their podcast and videos. She has a gallery on Deviant Art, which is part of the problem, because she also has access to the works of others that we consider inappropriate for kids. That is an ongoing issue and it isn't easy to deal with, because, like youtube, there isn't a lot of filtering that parents can control.
My son started a blog for Nintendo gaming when he was thirteen. He also produces a gaming podcast twice a month, which he hosts with his sister. He just started producing unboxing and review videos for his site so he has a youtube account. He buys and sells his games on eBay so he has both an eBay and PayPal account. He is also a ham radio operator and has turned his room into somewhat of a ham shack. He is very connected to the Internet for all of these activities. He is constantly on his laptop in his room to blog, edit his podcasts, do ham stuff and his homework (he is working on a school project now as I write this).
The downside is that he constantly has to deal with the dark side of the internet. Not long ago he and his sister had to perform a massive cleanup on his site from porn spammers. StopForumSpam went down during the night and the spammers hit the site hard, posting somewhere between forty and fifty graphic images in his forum. They were in the process of cleaning it up when I saw it. My son had a difficult time dealing with it. This was not something I was particularly trained to deal with as a parent and although I think I did the best I could, there really wasn't much I could do after the fact except counsel him about it. For those who don't have kids, it may not seem like a big deal, but it is. It's a parent's nightmare. I want to protect them from this sort of thing, but what can I do? Today's society won't let me. It actually works against me. As parents, we are still ultimately responsible for our children. Yet our hands are ultimately tied so that we can't do our jobs. Then we ultimately get the blame when things go wrong.
I don't have an answer for you, because my family struggles with it too. On the one hand, computers are a great tool for doing homework, learning new technical skills and honing natural talents. On the other hand, it's a window to a much darker world that can leave a permanent scar on a young, impressionable mind. It's a difficult time to be a parent.