Hi Lourdes, welcome aboard! One of the most fun things about Disney Cruise Line is the unique rotational dining as well as the fun evening attire.
You said you'd be sailing on the Wonder this August, which must mean you're headed north to Alaska! How exciting! You can be sure you'll need some warmer clothes for that sailing, but you will find the temperatures inside the ship to always be very comfortable.
On your seven-night sailing, you can expect one formal night, one semi-formal night, one Pirate Night, and the rest of the evenings will be cruise casual.
Pirate Night is a really fun evening on all four of Disney's ships with Deck Parties, special character appearances and lots of games and fun. Bring pirate gear and costumes for the whole family! We love to dress up in our pirate-y best that night! You will each receive a "Pirates IN the Caribbean" bandana that evening, but if you have costumes of your own, bring them! They are available for purchase onboard, but we always like to buy them at home and bring them along.
I hope this helps you plan your attire, Lourdes. Enjoy your Alaskan cruise!