People in Hawaii have adopted the Japanese custom of taking off your shoes at the door of a house. It makes sense when you think about what you've been walking through (ewww), and you'll feel more comfortable without shoes, anyway.
It is considered VERY gauche to enter someone's home with your shoes on. The line-up of shoes outside the door will remind you to remove them.
Bring a pair of flip-flops (called "slippers" in the Islands) along with you, and that will make the off-and-on process much easier. If you don't have any, visit Ala Moana Shopping Center; there's a shop there that specializes in slippers.
If you are fortunate to know someone on the island or get invited into a home, please remember to take off your shoes. There is a heavey asian influence on the islands, so most homes have a place at the doorway where you can remove your shoes or sandals before walking into the home. To leave your shoes on is considered very impolite.