Place the mandarin oranges, with their syrup, in a medium-size saucepan. Add the Champagne and bring to a boil. Reduce the heat and simmer until the mixture has reduced to about 1 cup. Remove from the heat and let cool.
Place the cooled mixture in a blender, and process until smooth. Stir in the sour cream, honey, and poppy seeds.
Toss the prepared fruit together in a large bowl, and pour the dressing over the fruit. Refrigerate for 1 hour. Decorate the fruit salad with flaked coconut or chopped nuts, and serve.