I really hope they give him a significant raise or it's going to be tough on you guys there.
It'll be a culture shock too, if you're not at all familiar with Asian cultures now would be a nice time for a crash course. Native Hawaiians aren't bad at all, unless you act like the stereotypical loud opinionated mainlander. You'll get plenty looks, but if you're open minded enough you'll fit in. Just don't go Waianae, should have no reason to anyway.
Always eat as much of everything as you can, be open minded and try new things. Never say you don't like something. Don't suggest they change or do things differently. There'll be some initial resentment towards you no matter what, take it in stride, some people will never warm up to you; they don't need or want you on their islands.
Beware the rumor mill. People are more apt to not say what they really think of you as not to stir the pot. Remember the nail that sticks up gets hammered down. It's better to be quiet and have people think you're a fool, then speak up and remove all doubt.
That's all I can think of. The wife's family has lived there for nearly 100 years now, well the ones that aren't native at least. She left Hilo 12 years ago for college and hasn't been back to the town since, as a frame of reference. She misses the culture and the food, but Hawaii isn't the 'paradise' it was 50 years ago. Her family lives a much better life on the mainland.
Either way, good luck with your new opportunity.