The changes you describe are very typical after pregnancy or significant weight loss.
Some patients have loose skin in the lower abdomen and sometimes it is above the belly button. Most patients also have some degree of rectus diastasis after pregnancy (looseness of fascia over and splaying of rectus abdominus muscles from the stretch of pregnancy). Some patients can even develop a small epigastric hernia in this area after pregnancy if there was extreme stretch on the abdominal wall.
All of these conditions are best corrected with a standard, full abdominoplasty. I prefer a very low incision from hip to hip that conceals the abdominal scar in most undergarments and swimsuit bottoms. This allows access to the entire abdomen for proper tightening of the myofascial (muscular) wall as well are removal and redraping of loose skin. If there was a small hernia discovered, it can easily be repaired prior to the plication or "tighting" stitches in the fascia (covering of the rectus muscles).
Some talk about "Floating the umbilicus" which means "disconnecting" the belly button from its stalk and resetting it in a lower position. In most cases, the appearance of the umbilical depression is changed and made too low, and that is not a technique that I recommend. Sometimes, there is a need to leave a small vertical incision with the closure but I have never had a patient that found this objectionable if it was necessary.
Another technique that some doctors advocate but I DO NOT RECOMMEND is a "reverse abdominoplasty" or reverse tummy tuck -- taking the "loose skin out" from the top and leave a large incision under the breasts. I do not perform this procedure because I think the scarring is more problematic and visible.
I think the best way to manage this problem is a standard, complete, or "full" abdominoplasty (Tummy Tuck).
I hope this helps!