Preheat oven to 350°F. Line 12 muffin cups with paper or foil liners.
Whisk whole-wheat and white flours, baking soda, salt, and nutmeg together in a large mixing bowl; set aside.
Add bananas, sugar-substitute and brown sugar, canola oil, milk, and egg to another large mixing bowl and beat or stir until completely blended. Pour banana mixture into the dry ingredients in mixing bowl and stir until just combined.
Fold in macadamia nuts and coconut. Fill each muffin cup using a 1/4-cup measuring cup. Bake until muffins are golden brown and tester inserted in center comes out clean (about 25 minutes).