Mix gelatins in a bowl.
Heat peach nectar to boiling, pour over gelatins, stirring until they dissolve; add ginger ale and pour into a 1-quart mold.
Cool, then chill until firm.
Unmold on a large platter.
Surround with peeled and pitted peach halves, hollow sides up (dip fresh ones in lemon juice to prevent darkening) and fill hollows with jelly.
Whip cream to soft peaks, drop by spoonfuls onto jelly, and top with cherries.