Carrieboo, I think the '2 children' magic number is because 1 child will replace each parent when they die, so the population is sustained but not increased.
I read today that the population around 100 years ago was 1.6 billion, and today it's 6.8 billion.
DH showed me a graph that shows the population from the last ice age to today - it was a steady, straight horizontal line at the bottom of the page, increasing very slightly around Julius Ceasar's time, then from Victorian time onwards it starts to go goes up, with today the line being vertical.
Also he said (he's a scientist) that we in the West are using 'three planets' worth of resources, balanced out by the much lower use of groundwater, oil, fish stocks etc etc by the rest of the world. But, nations like India and China are fast catching up, they want our lifestyle, and the Earth's resources just can't sustain our selfish and unsustainable level of living for everyone.
So, the answer is not to educate your four children privately, or to only take them for holidays in the UK, but to consider the bigger picture. The world needs to sustain frewer people in the long run, so that everyone can have enough.
Even now, small island nations are running out of fish stocks...