Harry Potter and the Repercussions of Future Past

Harry and Ginny Potter, happily married, are now entering a new phase of their relationship - parenthood. However, somehow, overnight the soon-to-be parents are transported 9 years back in time. Now they find themselves trapped in their 15/14 year old bodies with their memories intact, surrounded by people who are now younger and people who have been dead for years (both friends and enemies). Can the Potters tempt fate and destiny and can they once again undergo the Second Wizarding War, without changing the obvious?
Not to mention, with Ginny being pregnant, can they handle what appears to be a teen pregnancy?