Hey everyone,
Thanks so much for the advice! I ended up ordering the Sigma 50mm 1.4. It should be here tomorrow. I had the 430EX II in my cart, but decided to hold off on that for now. A lot of the things I've been reading regarding newborn photography has said to use only natural light, and no flash, if at all possible. If someone here feels differently, please chime in. (I was thinking that maybe once they start moving around I'd pick up the flash?)
I've got a place in my house where I think I can set up a little "home studio" that should allow some nice diffused light to come in. I might rig up some DIY lighting from Home Depot with "daylight" bulbs, and diffuse it with some bed sheets or something, make some makeshift reflectors, etc. I'll see what I can come up with. But I'm hoping to find a good slightly overcast day with enough light coming in that I don't need anything.