Hawaii is one of the most casual places in the United States and for almost all dress-up occassions, aloha attire is acceptable -- even de riguer. This includes weddings, business meetings, fancy dinners out, etc. Often for formal affairs, the invitation will call for "crisp aloha" which means dressy pants (rather than just dockers) and a tucked-in upper-end aloha shirt.
This is hard for visitors from the Mainland to grasp. Despite my insistence, many of my business partners still show up in jackets, dres shirts and ties. Some even persist in this behavior through multiple visits, though eventually they give in. Almost no one who works here lasts in Mainland clothing very long. There's something nice about not having to wear a tie to work!