Definitely see Fantasmic! Even if you don't get reservations for dinner,many here have had success with walking in and waiting, depending on when you visit.
We have always done the package at BD or H&V - figuring we have to eat dinner, anyway, and you get to use the "secret" entrance which is a long walk down!!
Worth it?? Definitely!! It's an awesome show - close tie with Spectro for our family!!And during FDP, I'd say book the package.