Emilia, so much fun is in store for you! With so many marvelous activities and experiences at Walt Disney World, sometimes time crunches happen.
Since you will be attending
Disney's Spirit of Aloha Dinner Show, exchanging your voucher at Disney's Polynesian Resort is probably the most convenient option. Head to the store Trader Jack's in the hotel lobby to complete your transaction. In the Magic Kingdom, the PhotoPass Sales Center is located in the Town Square Theater to the right after you enter the park. You will need a park admission ticket to reach this spot. Disney's Art of Animation Resort does not currently have a place to exchange a PP+ voucher for a card.
At the Spirit of Aloha Dinner Show you will find sundresses, khakis, and polos, but shorts are perfectly acceptable since many guests arrive straight from the parks. At Fulton Crab House you may also wear resort casual and will feel comfortable in slacks and a collared shirt, a dress, or more casual park attire such a shorts.
Enjoy your visit to Mickey!