Preheat air fryer to 350°. In a large bowl, combine cauliflower and oil; toss to coat. In batches, arrange cauliflower in a single layer in air-fryer basket. Cook until florets are tender and edges are browned, 10-15 minutes, stirring halfway through. In a large bowl, combine buffalo sauce and melted butter. Add cauliflower; toss to coat. Transfer to a serving platter. In a small bowl, combine dip ingredients. Serve with cauliflower and, if desired, celery sticks.