Don't bother with a compact camera; it won't give you what you want. A DSLR will give you a much better chance because of its focusing system, larger imaging sensor, and faster performance. You will still run into some missed shots because no camera can give perfect results automatically all the time...a camera is a tool, not a magic box.
Canon USA has the factory refurbished XS with lens for $399.99; at the moment they are including a free 2GB SD card and gadget bag:
Hello, I have read many posts and while helpful, I am still unable to decide. Here is what I am looking for: an affordable camera that functions fairly well in low light to capture images of a fast moving toddler. I am looking to spend somewhere in the range of $400, so I am in the mid-range for new point and shoots, or low range for a used DSLR.