I have tried to find an option for something similar to what you are asking, but I have never found a solution. I have a 10 year old I do not want to be able to download anything, at all. Nothing. Why?? Because he has this amazing ability to find older versions of things and istall them over my newer versions....no amount of "DON"T DOWNLOAD ANYTHING WITHOUT ASKING" seems to do any good because he does what he wants anyway....blah!
But the best I have ever been able to come up with is to make him a restricted user so he can't install anything damaging and I run Norton Internet Security which has options to restrict where he can surf based on the level I give permissions for....it's not quite as strict as I'd like it to be and somehow, he still manages to frag my comp up everytime he touches it...it boggles me...but he cannot get to porn sites and he hasn't done any damage to the OS itself since restricting him so I guess i got some of what I wanted....
If you get an answer to what you seek that works, I'd like to know so I can implement the restrictions as well.