Hello kitty, I must say I think its better not to have kids if your not ready than to have them because of a generic thing God said. What I mean with this is the following, in a perfect stste, God would like you to have kids, but if there is any reason you may not care for them as He would want you to, then don't have kids. He also said that people who cause kids not to believe in Him will get a worse judgement than most others. In the same way God would not have you marry just for the sake of it....even though that is how He intended us to live.
I find it interesting that you would foster but not have your own kids, do you mind saying why? (just interested)
I just read my post again and it sounds kinda harsh. I totally support it that you don't have kids if you don't want to. Its a big thing and you should be totally into it. Its a wise decision not to do things like this because of external preasure. It is between a husband-wife-and-God to decide.