Hi Lora!
I'm glad to hear your princess is heading to the
Pirates League for a Mermaid Makeover on your upcoming visit to await Disney World Resort. My daughter absolutely loved the experience when we visited last August, and I'm sure you will have a great time!
The Pirates League does offer some cute clothing options such as T-Shirts, Tutus and pirate themed costumes, however, when we visited, there were no mermaid costumes. Not to worry though, if you would like to purchase a full mermaid costume, you can make a quick pit stop on your way to the Pirates League on Main Street, or at Castle Couture to find a mermaid costume. You will be able to purchase two different Princess Ariel costumes - one is a Princess dress, while the other option is a two piece costume with a mermaid "tail" and purple top. That is the option my daughter insisted on having for her Mermaid Makeover last year, although I actually preferred the tutu and top from the Pirates League. Sizing shouldn't be an issue, I'm sure you will be able to find the Ariel costume with a practically perfect fit for your princess!
I hope you have a magical time on your Walt Disney World Resort vacation Lora! Please let us know if you have any other questions, we would be happy to help!
Stephanie