I feel your pain Ian. We too are expecting our 2nd child (due in late May). We don;t know what it will be, and we both like it that way.
We have settled on a few girls names, but we are stumped as for boys names. The ones that my wife likes, I don't like, and vice-versa. THe one boys name that we both agreed on was Sean, and that we used when our son was born. I told my son that since we liked the name Sean so much, we would name the baby Sean if it turns out to be a boy, and that we would call him (our son) "Hey You". To test this out, every now and then, I say "Hey You", and he always (never fails) says "What dad"? I then proceed to tell him that our plan to rename him is going off flawlessly, because he always answers to "Hey You".
The one boy name that we agreed on was Patrick, and my sister in-law sort of ruined that for me by saying that it would always remind her of Spongebob!