Preheat grill to medium.
Lightly brush fruit with oil and place on the grill. Cook until pineapple and plums are nicely caramelized, turning once, about 8 to 10 minutes. Remove to a plate. Meanwhile, in a medium bowl whisk together yogurt, honey and mint. Place 2 rings and 4 wedges on each plate and drizzle with dressing. Garnish with pine nuts.