A lot of us, including myself, have had or will have the rehearsal dinner at 'Ohana at the Polynesian Resort. Have you ever been there? The food is all-you-can-eat, served family style. It's delicious! 'Ohana means family so it's a great place for an RD. It is also very affordable, IMHO. Also, if you plan i right, you can see Wishes from the MK during your dinner. The only negative about having your RD at 'Ohana is that your group does not get a private room, you are seated in the restauarant with everyone else. They try to seat you as together as possible.
Good luck, I'm sure there will be a lot more good suggestions