Its darn hard to have a baby. Being a man, I can't say that I've done it, but my wife is currently 7 months pregnant with our second child (a boy). Physically, she has had a variety of health problems caused by this pregnancy (esp back problems). Bearing children isn't easy, and I think that given the choice, most women will opt for fewer rather than more. And nowadays, they have a choice.
Kids used to be the mechanism that people used to save for their old age. The capital which was spent raising them was returned as profit when you were an old koot and they had to take care of you. Now people can just use 401K's instead....which require a lot less diaper changes (unless the market collapses...then you may need to change your own diaper).
Feminism is partly to blame as well. Its no accident that Hillary only had one child. Many women believe that their real purpose in life lies in the professional/work world. Children are a hinderance to obtaining that law firm partnership. This is especially bad in that it disproportionately affects high IQ women.
But I think that one of the major causes of this trend is the materialism inherent in modern "McWorld" culture. Our consumer/producer oriented society boils everything down to a transactional, profit-loss relationship. Children are bad because they hinder the efficiency of this system, and are thus discouraged. Everyone knows that for all of the "family friendly" policies of various corporations, they all basically view such relationships as a nuisance. As they used to say in the Navy "If we wanted you to have a family, we'd have issued one to you".
Companies reward those employees who are most compulsive about their work...which means they reward those who spend the least time with their families. And less kids require less time.
Our economic and social system boils down to this: Work all the time, spend all your money on worthless consumer goods, max out all of your credit cards, and have no kids which distract from the cycle. And when you die, you can be replaced by a new cohort of immigrants to begin the cycle again.
Problem is...when this system extends everywhere, where will the new immigrants come from?
Also, humans are not interchangeable robots. They have culture, religion, etc. You just cannot import vast new populations to replace your existing, sterile one and not expect to suffer major dislocations.
The issues of populations, immigration, and differential growth rates, will dominate this century...and it may not be pretty.
I agree with much of what you have said. Congratulations upon your planned New Years' event! I'm a father of four myself, and , yes, cuss myself every day for the time I'm not spending with the kids(as I sit here Freeping). It's just one of those things, though, man-- you either buy into the parent thing and say, yeah, this is what we chose to do, and God willing, we're going to--hang the rest of the stuff; or you don't. But note that these devices that are sitting on our desks, and have made this kind of discussion possible, really will impact the future and our ability to spend time with the family, maybe even more so now with anthrax blowin' in the wind.