Hi Terry,
Disney World is an awesome place to celebrate a birthday & its wonderful that you are planning ahead to make this an extra special day for your daughter!
Currently, Guests can meet Ariel in her human form at the Adventureland Veranda Gazebo at the Magic Kingdom (MK). She along with other characters from the Little Mermaid appear intermittently throughout the day.
You can also see Ariel in the
Celebrate A Dream Come True Parade held most afternoons in the Magic Kingdom.
Be sure to check the
Times Guide when you enter the Magic Kingdom for appearance times for Ariel and other character greeting.
Ariel has also been known to appear at
Cinderella's Royal Table at the MK & the
Akershus Royal Banquet Hall in the Norway Pavilion in Epcot. There are no guarantees which princesses will appear - it varies - but either of these places would be a great dining location to celebrate a birthday.
Wishing you many magical memories :-) Allison