In reply to goose299:
Fantastic news: congratulations to you both. You're also entering a whole new world of kit (hint: spotty otter down suits are available cheaply on eBay, or are permanently on discount sale somewhere).
I recommend the macpac kiddie carriers - expensive, but worth it. First trip out with my then-ginormous six-month old, we did nine miles comfortably.
Oh, and don't be afraid to buy second hand......
Martin