Hi Dawn,
What a busy day you are going to have! You are going to have an exciting start to your vacation!
The best place to exchange the
PhotoPass+ voucher that is outside the park is at Downtown Disney. There is a guest services center which will exchange the voucher and allow you to start taking photos right away.
You can grab a bus to Magic Kingdom and then walk to the Contemporary Resort for dinner at
Chef Mickey's. Your dinner should last about 60-90 minutes depending on how fast you eat and the characters' rotation through the restaurant. Since it is a buffet, it does move along at a nice pace.
You then can head to your
Pirates & Pals Fireworks Voyage. I think this is the best way to see the fireworks at Magic Kingdom. It is especially nice if you have someone who does not like the noise of the fireworks as you can not hear the noise from the water. You only hear the sound of the music.
Wishing you a magical vacation!
Beth