1900 PF is hosting Cinderella's Royal Feast, so that may affect your decision. We have that booked on our daughter's birthday. For what they're charging, ($24.95 per adt) they should have at least one other princess there. We're going because it was the only princess meal we could get all week. I'm still hoping to score a cancellation at the Epcot Princess Storybook b-fast.
If you schedule O'hana right, you can watch fireworks from there or walk down to the beach of the Poly and wait for them as well as the electrical water pageant.
These both sound like great options to kick off your vacation. Let us know when you decide.