I'm far from an expert, but I have heard/read that one successful pregnancy increases your chances for more with PCOS. I couldn't tell you by how much.
I tried for nearly two years to get pregnant (other than a 6-8 week m/c - no success). As soon as I decided I was too old to try to have that "one last baby" (I have two others from before my diagnosis), gave up, and started to lose weight for mere health's sake, I conceived. My risk of miscarriage was the same as anyone with PCOS, but I have successfully made it to 13+ weeks and am now at "normal" level of risk for m/c, according to my OB.
If you are prepared (or at least as prepared as one can be) for the risks, and everything else is in place, so to speak, I say go for it. But be prepared to be ready for bad news. Be ready for anger, frustration, pain, sadness and even, hopefully, elation. Be ready to be there 100% for your wife. But since you have one child already, you probably know this
