1. Preheat oven to 400 degree F and lightly butter 2 large baking sheets.
2. Whisk together flour, 1/2 cup granulated sugar, the baking powder, and salt in a large bowl. Add butter and, using fingertips, rub into flour mixture until it resembles coarse crumbs. Using a fork, stir in 2 cups plus 2 tablespoons half-and-half just until a dough forms; transfer to a lightly floured surface. Pat dough into a 10-inch disc (1 inch thick). Using a 2-1/2-inch biscuit cutter, cut into rounds, repatting scraps to make 17. Transfer rounds to prepared pans, placing 1 inch apart, and brush tops with remaining 1 tablespoon half-and-half. Sprinkle tops with sanding sugar and bake in upper and lower thirds of oven, switching positions halfway through, until golden brown, about 25 minutes. Transfer shortcakes on sheets to racks to cool.
3. Meanwhile, toss blueberries with lime juice, lime zest, and 1/4 cup granulated sugar in a large bowl. Toss strawberries with lemon juice, lemon zest, and remaining 1/4 cup granulated sugar in another large bowl. Let both stand 20 minutes at room temperature.
4. To serve, horizontally cut shortcakes in half, add a dollop of whipped cream and berries to bottom halves, and cover with tops. Makes 17 servings.