What type of exercise for "mommy belly?"?

I am in decent shape for my age (30) and having two kids 23 months apart. I have upper abdominal muscles which looks like a soft "4 pack." I can't figure out what type of lifts or crunches I can do to flatten out the bottom portion of my belly, right above the pelvic area. It is still squishy, jiggly and I am just frustrated at this point. Any thoughts on how I can target this area better?