I agree with the 17-55. My neighbor has it and it hardly ever leaves the camera. I personally got the EF-S 15-85 f/3.5-5.6 instead because I preferred the greater focal length range over the constant 2.8 aperture, but my kids are older and most of my pictures are outside. With a newborn I suppose you will take more pictures inside where the larger max aperture will be a greater advantage. It will also allow more nice background blur.
I would also add an external flash before you add a tele, the 430EX II is a great choice. It makes a huge difference over the built-in flash.

Arnt