that you're aware of this and considering it before expanding your family.

Think about it....some people are still doing nothing (or next to nothing!) to reduce their envir. footprint on this planet.  Meanwhile,  you  are putting up for consideration one of the most important decisions a family can make in terms of what this will do to the environment.  I find that admirable.

Ultimately its your choice (obviously) but I disagree with the pp that finds the idea of smaller families being pushed by environmentalist as offensive.  I don't at all.  I think its common sense.

We have one child and are not considering more.  But thats simply a choice we made that accidentally conforms to our 'green' beliefs.  If I felt differently about my family's size I would be conflicted about it too.

good luck with your decision.  (btw, I think adoption is a wonderful option too)