Divide the grapes into the bottom of 4 parfait glasses. Spoon one-eighth of the yogurt over the grapes. Divide the mango pieces evenly on top of the yogurt. Spoon the remaining yogurt on top. Sprinkle the top of the parfaits with 1 tablespoons each toasted pumpkin seeds and crushed amaretti cookies. Serve the parfaits immediately or refrigerate uncovered for up to 1 hour.
To toast the pumpkin seeds, arrange in a single layer on a baking sheet. Bake in a preheated 350 degrees F oven until lightly toasted, 3 to 5 minutes. Cool completely before using.