Line a baking sheet with parchment paper and set aside. Preheat oven to 400 degrees. F
In a large bowl, stir together flour, baking powder, 1/8 tsp cinnamon, nutmeg, salt and 1/4 cup granulated sugar. Cut in the butter. Stir in the milk until the mixture turns to dough. Pat the dough into a circle about 1/2- inch thick.
With a 2 1/2- inch biscuit cutter or glass with a 2 1/2- inch opening, cut 6 circles of dough and place on the parchment lined baking sheet. Re-form the remaining dough into a 1/2- inch thick circle, cut 4 more biscuits and place on the baking sheet. Stir together the turbinado sugar and 1/8 tsp cinnamon and sprinkle over the cut dough. Bake about 17 minutes, remove from oven and transfer shortcake rounds to a rack to cool. (Note: shortcake can be prepared 24 hours in advance.)
In a large bowl combine the strawberries, peaches, granulated sugar and Grand Marnier. Refrigerate for at least 1 hour; stir occasionally.
Cut each shortcake in half horizontally. Line a 2 1/2- quart trifle bowl with the shortcake bottoms. Using a slotted spoon, transfer all of the fruit to the bowl and evenly spread over the shortcake. Arrange shortcake tops over the fruit. Pour the remaining fruit juice over the top. Cover and refrigerate up to 6 hours.
Pour the whipping cream, powdered sugar and 1 tsp Grand Marnier into a bowl and beat until soft peaks form. Spoon over the shortcake. Sprinkle with Turbinado sugar and serve.