You are right, of course, that it has to be a collective effort. However, your mental mistake was in saying that nothing you do will matter. I absolutely agree with you that bringing our population (globally!) under control is the most important step we can take. I absolutely agree that the rate of growth of our consumption of fossil fuels is going to cause us to hit a "brick wall" in, AT MOST, a handful of generations -- if it doesn't happen to your kids, it'll happen to your grandkids, I'm almost certain.
This brick wall is basically the point beyond which, obtaining cheap fossil fuels for electricity production and transportation at a rate that meets demand is impossible. In 5 year old terms, "everything will start getting extremely expensive." I have no idea what is going to happen at that point. Resource wars? Massive investments in nuclear power and electric cars shore up "business as usual" for another few decades? Fusion power becomes economical and saves us for the long haul, provided that we're all willing to convert to electric cars? I don't know. I just know that it's going to be bad, especially in the short term, as food prices spike and people can't pay their gas bill to get to work (if the gas station even *has* any gas).
When it comes to matters like this, every little bit DOES help. Every person who is convinced that they need to do their part by conserving as much energy as they can is setting an example for the rest who are happy to keep rollin' coal.
In your situation, by far the greatest damage you've done to the planet and our collective resource supply was to bring those three children into the world. United States citizens consume more fossil fuels per capita than all but 12 countries, but most of those countries have extremely small populations with high median income, so they're hardly a drop in the bucket. I guess you could have done worse by raising them in Qatar, but it's still pretty bad.
Honestly, I could care less about your SUV. I'm not one of those wackos who would try to force you into an abortion when you had more than 2 kids, and I certainly wouldn't want any harm to come to them now that they're a part of the world.
All I want is for you to *accept responsibility for your own choices and actions*. If you're willing to man up and admit that you *could have*, in retrospect, contributed less to the world's problems by *not* having 3 kids (and having, instead, 2, 1, or 0), and if you're willing to carry forward the message to others that the need is urgent to ensure that *everyone* contributes a little bit to making the population problem better, and NOT worse (which is unfortunately what you've done, whether you think it's significant or not), then you're on the right path, SUV or not.
I know that we can't all be ideologues and that sometimes we can't practice what we preach because of the realities of life. I don't know you, and for all I know your children were "a coincidence" (not planned) and were triplets, which can happen to anybody. But taking responsibility for yourself is a necessary prerequisite before you can start telling other people (such as the China you harp on about -- and rightly so) that *they* also need to quit reproducing like rabbits and cut down on fossil fuel consumption. Otherwise they'll just laugh at you, point at your 3 kids, and go get their wife preggers tonight to make the problem worse.