We spent a week on Maui and both of us need to eat gluten free, as well as some other food intolerances. We cooked our own food in our condo 95% of the time for safety.
For gluten free groceries, our best bets were Foodland Farms in Lahaina, and the Farmer's Market in Honokowai. A Safeway is nearby in Lahaina, but we did not shop in that one.
There is also a Costco and Whole Foods 1 hour away in Kuhului but we did not check them out this trip.
There were several decent gluten free items available, such as crackers, rice cakes, Bob's red mill mixes and applegate farms lunch meat, but we could not find any gluten free bread. Foodland farms had gluten free wraps made by the Tortilla Factory, so those had to do. We also could not find any gluten free steel cut oats, which I love to have for breakfast. Luckily, I brought a bag of those with me.
Bamboo Fresh is a small hippy-ish cafe in Lahaina that was very helpful with lots of suggestions. They have gluten free wraps, salads and ricebowls available and use quality local ingredients when possible. We ate there and had no problems.
There are many eateries in the area. Due to previous gluten problems eating out, we try to avoid that in general. I found it interesting that the few places we wandered into to browse seemed to be accomodating on the surface. After reading their gluten free menus we were scared off by the disclaimer that all items are prepared in the same area as gluten containing foods.
We also took a tour to Hana with Valley Isle Adventures. They provide a sit down lunch in a remote location where there are no other food options. After talking to the booking person, I was satisfied they could actually provide us with gluten free meals, which they did.
The driver heats and serves a prepackaged lunch. For those needing gluten free, they served a naked but brined and delicious chicken breast packaged separately while the others had BBQ chicken. The chicken was cold since it could not be heated on the contaminated grill, but we did not mind at all! Individually packaged fruit salad substituted for the pasta salad served to others, and we had a separate vinaigrette dressing for our green salad.
We did not even check out some of the high end restaurants in the area. In general, it seemed that many of the resorts were at least acquainted with gluten free requests and if no gluten free options appear on the menu, it's a good idea to ask.
We have learned to err on the side of caution when it comes to restaurant dining. It only takes one person having a moment of distraction to contaminate your food and potentially ruin the rest of your trip.
Since we spent most of our time outside having fun, the plan was to stock up on safe groceries and not spend a lot of time researching restaurants. We succeeded and had a great time! There may be lots of gluten free options in the Kaanapali area that we did not find. In the end, we had a safe trip and ate reasonably well. But if you are looking for a French Laundry type of experience where the staff has thoroughly developed an absolutely delicious ( and creates an almost moved to tears experience) Gluten Free menu, just so you too can have an awesome meal, it probably won't be on Maui.