Cook the acini di pepe pasta according to package instructions; drain and let cool.
In a large mixing bowl, combine the cooled pasta and crushed pineapple.
Add the mandarin oranges, mini marshmallows, and shredded coconut to the bowl.
In a separate bowl, whisk together sugar, milk, and vanilla extract until smooth.
Fold the whipped topping into the sugar mixture until well combined.
Pour the creamy mixture over the pasta and fruit; gently stir to combine.
If desired, add chopped nuts for extra crunch.
Cover the salad and refrigerate for at least 2 hours to allow flavors to meld.
Before serving, stir the salad gently to ensure even distribution of ingredients.
Garnish with additional coconut or fruit if desired, and serve chilled.