When we went to MGM, prior to Fantasmic we dined at Sci Fi. The resturant is totally decked out and although it's not a part of the Fantasmic Package, it was fun! We got to Fantasmic an hour early and my daughter made a bee-line for the middle seats. We thoroughly enjoyed the dinner and the show.
Mama Melrose's has the Fantasmic Package but they are on the other side of the park! LOVED their food though!!
As far as the live Cinderella... Cinderellabration is going on in front of the castle. When you enter the Magic Kingdom you'll get the insert which will specify times for the day you're there. It's right in front of the castle and her princess friends join her. Beautiful show!