Hi,
I just got off the 4-night Wonder and they did have hair braiding.
They told me that reservations were made at the Treasure Ketch. The braiding was done at poolside. They also had braiding at Castaway Cay. I did not see it in our navigator and really wish that I had our girls done. It was 2.00 per cornrow and 1.00 per braid and 50 cents extra for long hair per braid.
Hope this helps. If you are planning on doing it, I would inquire at guest services as soon as you get on board.