In a large bowl, combine the pineapple, oranges, bananas, strawberries, coconut, and lemon juice. Add in the mini marshmallows and mix gently.
In another bowl, whip the heavy cream with a mixer until it starts to thicken. Add the vanilla extract, then gradually mix in the powdered sugar and cornstarch. Continue to whip until stiff peaks form, about 5 minutes. Gently fold in the yogurt.
Combine the whipped cream mixture with the fruit mixture. Stir gently until everything is evenly coated. Refrigerate until ready to serve.