Preheat the oven to 425°F (220°C). Line two 12-well muffin pans with about 16 paper liners and set aside.
In a medium bowl, stir together the flour, baking powder, cinnamon, ginger, nutmeg, and salt and set aside.
In a large bowl, using a whisk, mix together bananas and brown sugar to combine. Slowly add the oil while whisking. Then, add the eggs and whisk to combine. Add the pineapple juice and vanilla as well. Then, add the flour mixture and whisk until thoroughly combined. Finally, add the carrots, pineapples, and coconut flakes and whisk just to incorporate and set aside.
In a medium bowl, use your fingers to combine the flour, brown sugar, oats, cinnamon, and butter until the mixture is crumbly. Do not overwork; otherwise, it will become a paste rather than crumbs.
Spoon the batter into the prepared wells until almost full and top with the streusel. You will end up with about 16 muffins. Bake at 425°F (220°C) for 5 minutes. Then, leaving the oven door closed, lower the heat to 350°F (175°C) and bake for another 11 to 13 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Remove from the oven, let cool in the pan for 15 minutes and then transfer to a wire rack to cool completely before serving. Store in an airtight container at room temperature for 1 day, in the refrigerator for up to 3 days, or freeze for up to 2 months.