For the cobbler: Preheat the oven to 425 degrees F. Using 1 tablespoon of the butter, grease a 9-by-13-inch baking dish.
Chop the remaining 2 tablespoons butter into 1/2-inch cubes and set aside. In a separate bowl, add the flour, sugar, baking soda, salt and eggs. Mix together with a wire whisk until the dough just comes together.
Add the blueberries and peaches to the greased baking dish. Drizzle the top with the lemon juice, sprinkle with the cinnamon and top with the remaining butter cubes. Drop the dough in large pieces onto the mixed fruit. Bake until the biscuits are just browned and the fruit is bubbling, 30 minutes.
For the whipped cream: In a large, chilled stainless steel bowl, add the whipping cream, sugar, vanilla and cinnamon. Using an electric hand mixer, beat the cream for 1 minute on medium high. Place the bowl in the refrigerator until ready to serve.
To serve the dessert, spoon some of the warm cobbler into a bowl, and top with a dollop of whipped cream.