Line a baking sheet with wax paper and spread the mango and berries on it in a single layer. Freeze just until the fruit is slightly firm, about 20 minutes.
Just before serving, combine the banana, agave nectar, lemon juice and ginger in a blender and pulse until pureed. Add the cream and pulse several times until softly whipped. Spoon the fruit into glasses, dollop the banana cream on top and serve.