Frozen Orange Creamsicle Pie with a Pretzel Crust

For the crust:

salted pretzels, finely crushed in a blender or food processor

sugar

butter, melted

For the filling:

heavy cream

powdered sugar, divided

vanilla

cream cheese, at room temperature

frozen orange juice concentrate, thawed

Additional whipped cream, orange slices, and mini pretzels (for garnishing), if desired