No, I don't think there should be a restriction on number of children. I have 5. Do most people have 5? No, of course not. Most people have 2, or at the most 3. So the argument is ridiculous because the majority don't have large families anyway (in the western world). In third world countries it is a different situation because people use much much less than what we use, anyway.
The argument about population causing stress on the world's resources is legitimate, but I also think that consumption has an enormous role to play in the debate, because we in the western world are much bigger consumers of just about EVERYTHING, than anyone is the developing world.
Perhaps the question should be about whether we need all the stuff we have?
*sorry if you read the first post of this, a crying child hit lol.