- In a large mixing bowl, whip the heavy cream until soft peaks begin to form. Gradually add the powdered sugar and vanilla extract, continuing to whip until stiff peaks form (approximately 3-4 minutes with an electric mixer). 
- Gently fold the sour cream into the whipped cream using a rubber spatula. If using Cool Whip, fold this in as well. Use a gentle folding motion to maintain the airy texture. 
- Fold in the mini marshmallows, ensuring they're evenly distributed throughout the cream mixture. 
- Add the well-drained pineapple chunks, mandarin oranges, strawberries, and halved grapes to the cream mixture. Fold gently to combine. 
- Gently fold in the shredded coconut and optional chopped nuts until evenly distributed. 
- Transfer the mixture to a beautiful serving bowl, cover with plastic wrap, and refrigerate for at least 1 hour—though 4 hours or overnight yields the best flavor development. 
- Just before serving, garnish with maraschino cherry halves and a light sprinkle of additional coconut if desired.