L.B.
Hmm, South Mississippi -
I live there.
Southern most Mississippi is the Gulf Coast - 26 miles of beaches - check out the beach and pier in Ocean Springs - very nice, casinos, some family amusements. WWII memorial; the Lynn Meadows Discovery Center in Gulfport is great fun for little ones, Mary C O'Keefe Cultural Center, Seafood Museum, Ohr Museum, and there is more.
Another place that my son and I enjoyed is Vicksburg, Ms - right on the Mississippi River at the Louisiana state line. Civil War battlefield park - nice self driving tour through the park - huge monuments, and lots of places to stop and let little run. Fun water side area with a splash pad and cool mosaics, - just a pretty little town.
http://web.vicksburg.org/vicksburg/default.aspx
If you go a little farther north - south central Mississippi - there is Hattiesburg - it has a lovely little zoo that is free (or under $5).
http://www.zoohattiesburg.com/html/plan.html
If you go to Central Mississippi - you hit Jackson, our capital. Planetarium, Zoo, Natural History museums, and more.
Okay, I am not going farther north than that b'c it would be way out of your way. LOL
Oh, gosh, I feel like a tour guide.
Whatever you do - enjoy your trip !!!!