Ellen had a question about some relatives moving to Hawaii, and was there anything they should take that's hard to get there? (In the future, dudes, I'm more than happy to offer advice like this privately, but you've gotta give me a way to get in touch with you.)
It depends a lot on where in Hawaii they're going. Oahu is pretty darn urban, thanks to Honolulu being there. I'd say you can get anything there that you can get on the mainland. Plus a whole lot else besides. The outer islands, you can still get everything the mainland has to offer, but it may take the wonders of mail order, and take some time. The Big Island (named Hawaii) has quite a few 'chains', like book stores and home improvement places and decent grocery stores, but you may have to drive a good bit to get to them. Maui is much the same; you can buy almost anything there but you may have to drive a while. Kuai and Molokai are pretty damn rustic and you may be looking at mail order for a lot of things, even everyday stuff. (A local kid once told me 'There's nothing to do on Molokai but smoke weed and surf.')
On the flip side, if your family enjoys Asian food, they've landed in heaven. And the coffee is really good and really affordable. The community college system affiliated with University of Hawaii is wonderful, if anyone's going back to school.
Culturally, if you look at the whole thing as a fun adventure, it will be. But if you go there and get mad because it isn't just like home, you'll never be happy, because it's NOT just like home.
Oh - if they're on Oahu, tell them to hit the Aloha Stadium flea market for clothes, jewelry, and 'tourist stuff'. It's not like a mainland flea market. It's more like an outdoor shopping mall.