1. Preheat oven to 350 degrees F (175 degrees C).
2. Brush chicken with olive oil, salt and pepper. Wrap in foil and bake in the preheated oven 1 to 1 1/2 hours, until internal temperature has reached 160 degrees F (70 degrees C).
3. Remove chicken from heat. Cool, debone and chop.
4. In a large bowl, mix chicken, mayonnaise and dill. Gently fold in grapes, mandarin oranges and sunflower seeds.
5. Spread the mixture on miniature croissants. Cover and chill in the refrigerator until serving.