I was just on Maui and had the treat of going to Hawaiian Moons health food store (I think that's what it was called). Tons of gluten-free products, same prices as mainland Whole Foods for the most part.
Incidentally, my DH came across this good review of Celiac and Princeville on Kauaui: http://www.tripadvis...HECK_RATES_CONT
I think you'll have a great trip! Give us a great post-trip report so we can follow in your footsteps!
There is also a Whole Foods in Maui