Position an oven rack in the center of the oven and preheat to 350°F (175°C). Grease two 8 1/2 x 4 1/2-inch loaf pans well with nonstick cooking spray or softened butter, making sure to coat the corners.
Line each pan with a strip of parchment paper, leaving a little overhang on the long sides so you can lift the loaves out easily after baking. Set the prepared pans on a baking sheet if you like.
Peel the bananas and place them in a large bowl, then mash them with a fork or potato masher until mostly smooth with a few small lumps remaining. Measure out 2 cups of mashed banana.
Pour the crushed pineapple into a colander or fine mesh sieve and press gently with a spoon to drain off as much juice as you can. Roughly chop the macadamia nuts into small, pea-sized pieces and set them aside.
In a second large bowl, add the 3 cups of flour, 1 teaspoon baking soda, 1 teaspoon salt, and 1 teaspoon ground cinnamon. Whisk everything together for about 30 seconds so the baking soda and spices are evenly distributed.
To the bowl of mashed bananas, add the 1 1/2 cups of sugar and the 3 eggs, then whisk until well combined. Pour in the 1 cup of vegetable oil and whisk again until the mixture looks smooth and glossy.
Stir in the well-drained crushed pineapple, 2 teaspoons of vanilla extract, and the coconut extract if you're using it.
Pour the dry ingredients into the bowl with the wet ingredients. Use a rubber spatula to fold the mixture gently, scraping the bottom and sides of the bowl, until you no longer see dry flour. Stop mixing as soon as the batter comes together.
Add the chopped macadamia nuts and 1 cup of sweetened flaked coconut to the batter. Fold gently with just a few strokes until the nuts and coconut are evenly spread through the batter.
Divide the batter evenly between the two prepared loaf pans, filling each about two-thirds full. Smooth the tops lightly with the back of your spatula. Sprinkle the remaining 2 tablespoons of flaked coconut evenly over the top of both loaves.
Place the pans in the center of the oven and bake for 55 to 65 minutes. If the tops start to brown too quickly after about 40 to 45 minutes, loosely tent the loaves with a piece of foil. Check for doneness by inserting a toothpick into the center of a loaf, which should come out clean or with a few moist crumbs attached.
Let the loaves cool in the pans for 15 minutes so they can set up. Use the parchment overhang to lift each loaf out, then transfer them to a wire rack to cool completely. Slice each loaf into 12 slices with a serrated knife, using a gentle sawing motion for clean edges.