Plunge the peaches into a large pot of boiling water for one minute; using a slotted spoon, transfer them immediately to a large bowl of cold water. The skins should slip off easily. Slice the peaches. There should be about 1 1/2 cups. Sprinkle gelatin over the 1/4 cup of cold water in a small bowl. Set aside. Combine 1 cup prickly pear juice with peach slices and prickly pear pieces in a medium saucepan. Simmer over low heat for five minutes. Turn off the heat under the fruit and strain off 1 cup of juice. In a small saucepan, combine the juice and honey and cook gently just at a simmer for eight minutes. Add the softened gelatin and lemon juice to the honey mixture and stir until gelatin is dissolved. Puree the fruit and remaining juice in a blender. Combine with the gelatin and honey mixture and freeze in a bread pan or similar container. When nearly hard, remove from freezer, transfer to a bowl, and beat with an electric mixer. Beat the whipping cream until stiff and fold into the fruit mixture. Return to the bread pan. Refreeze until firm.