Daughter was Ariel with a garage sale costume with added fabric paint and store bought wig.
Son was Flounder in a custom made costume that was sold on ebay to recoup some of the expense.
Mom was Sebastian the Crab (actually a giant Lobster but who could tell) bought on ebay and resold on ebay.
Dad was King Triton with a custom made tail and white wig and beard. The wrist bands were Koozies cut and painted gold. The crown was a piece of foam cut and painted gold and bobby pinned to the wig.
Thanks to the Holt Family for this great idea!