Howdy Nichole!!!
I love this question!!! What a fabulous way for you to celebrate Halloween!! Your son will absolutely LOVE
The Pirates League!!
My son was transformed from a simple 3 year old from Texas into a decked out Captain Jack Sparrow last year! He loved every minute of it!
I have wonderful news for you! You do not have to pre-purchase the Captain Jack costume prior to your visit. We purchased my son's costume when he was at Pirate's League. There is an additional charge on top of the package price but you are able to purchase it there. For more information, you can call 407-WDW-CREW.
I do want to extend one word of caution. Although the Captain Jack costume is available for purchase, there is a chance that they might be sold out. I would be devastated for you if your son was not able to get the costume he wanted. I have been told that it is rare that this happens but I want you to at least be aware that there is a small chance it could happen. I know you are trying to keep your packing to a minimum but you might look into purchasing the costume prior to your trip or start looking for it when you arrive at Walt Disney World to be sure you have it when he goes to Pirates League. I don't want to cause alarm, I just want to ensure you have as much information as possible so you can make the best decision regarding his costume.
I'm so excited for you and your first mate!
Thanks so much for your question and please let me know if you need any further information. Have a magical day!