My comments would be... your 3 year old needs a little training. ;) If the dog is being dominated and man-handled, then of course submissive behaviors will follow. You need to keep a closer eye on the way your three year old treats the dog before the problem gets worse. Otherwise the dog may end up with a lifelong fear of young children.
If the problem is already deeply set in, there are steps you can take to reverse the behavior, but it isn't easy. It would involve a process of desensitizing the dog to your three year old, or anything else that leads to unwanted urination. This process is outlined in my ebook
