Hello, Karen!
What a great night you have in store for you!
While many restaurants in Walt Disney World will have you in and out in about an hour, I'd book the 5:30 reservation at The Wave, just to be safe. You'll want to arrive at the
Pirate and Pals Fireworks Voyage a little early, and you won't want to have to have that start time on your mind as you enjoy your dinner. Keep in mind, too, that Advanced Dining Reservations are made on what's known as a "Table Management System," so you could be seated a little later than 6:30 with that first reservation, which might then cause you to want to race through what would otherwise be a really lovely, relaxing meal.
Have fun on your PIrate and Pals Fireworks Voyage! My family is so excited for our upcoming Voyage, so I'm sure yours is, too!
Send more questions as you think of them! I'd love to help!