I have never liked the idea of thinking of children as liabilities. I feel even more strongly now that children are assets. Sure, they can put a strain on your finances, but anything worth investing in is, right? And hey, so what about saving money for the kids college fund? Invested correctly, that's money well saved.
In my opinion, having children is the best thing you can do for the world. Invest strongly in their education, their health, and personal well being. While you may not get rich having kids, investing in the future of the world is its own reward.