Place one of the vol-au-vent shells on a lightly floured surface. Roll with a rolling pin until about 5 inches in diameter. Place on a large non-stick or parchment-lined baking sheet. Repeat with remaining vol-au-vent shells.
Place baking sheet in the fridge until tart toppings are ready.
Cut the mangos in half and peel off the skin. Cube 1/2 a mango and place in a food processor with the rum. Puree until smooth. Slice the remaining 1-1/2 mangos.
Preheat the oven to 375 degrees F. Divide, spoon and spread the top of the vol-au-vent shells with the mango puree. Arrange mangoes slices on top; sprinkle with coconut. Bake 20-25 minutes, or until puffed and golden. Melt the marmalade in a small pot with 1-2 Tbsp water. Brush and glaze the tarts with marmalade. Serve tarts warm or at room temperature.
Note: Ginger marmalade can be found in the aisle other jams are sold.