Instead of coconut, try chopped pecans as a topping for the potatoes.
The moistness of sweet potatoes varies by color. Lighter sweet potatoes have a drier texture, so you may need to add milk or water when mashing them.
Put the mashed potatoes in a microwavable dish, cover and refrigerate. Make the topping and store at room temp. To serve, microwave the potatoes, loosely covered, on High for 10 to 12 minutes, stirring several times, then sprinkle with the topping.