Slice the peaches and add to a medium bowl. Sprinkle with a teaspoon of lemon zest, a couple of tablespoons lemon juice, and sugar. Let the peaches sit for 5 minutes, then gently stir in the mint, if using, and the berries.
Halve the cantaloupes and trim the bottoms so they sit flat. Scoop out the seeds and fill with ice cream or sorbet and the Melba topping.