You cant fail with a nicer sundress and wedges or fancy flat sandals, my personal favorite
You can get creative with the catering too, using red and white striped circus-style catering stalls
I loved wearing knit dresses and layering jackets
Consider your look sorted
Dreaming of the forbidden human world beyond the surface, she had always longed to be part of that world, and made a deal with the evil sea witch, Ursula, garnering herself a pair of human legs but also losing her voice and the ability to speak as part of an effort to be with Prince Eric, whom she had saved from a ship disaster earlier in the film
similar option If you do not have a black dress in your wardrobe, you can choose other dark-colored dresses that are simple and modest