Too Much T.V.?

I will be the first to admit that I believe my kids watch too much t.v. They also spend too much time on the computer. And they probably don't get enough exercise outdoors. So now that I have thoroughly exposed myself let me try and redeem. I have cut down considerably on their computer time by blocking their account page from them. They have to earn their computer time, unless it has to do with homework. The t.v. stuff we are working on, as well as trying to get more outside time. I try and limit the amount of t.v. the kids are watching, and I absolutely limit what they watch. My daughter likes to watch the ever popular Nickelodeon shows..such as Dora the Explorer, Diego, Ni Hao Kailan (sp?), etc... and she can speak some spanish and chinese now because of it. She regularly uses Spanish with me (vamanos mama, vamanos!) So since she hasn't started preschool yet I consider this educational and therefore it is allowed. But really how much is too much. Do I allow only 1 program (30 minutes)? Do I allow them to pick out up to an hour's worth of programming? Do I allow more if they spend some more time outside or doing chores? Maybe a combination of all of that. I do know that the current level of television watching is just not acceptable to me anymore and something has to change. I will keep you posted as to what has been decided.