I would also pick Navy, like the night sky. As far as quilting it, stitch in the ditch would be fine, but when you run into those joins where all 6 triangles come together, it might be too bulky for your machine. I would stitch 1/4" away from the seam, on both sides of the seam. It is twice as much quilting, but with a baby quilt you want it to be sturdy. If you have a walking foot for your machine, this would be the place to use it.
Your quilt is wonderful. Great fabric choice!