Start by slicing the cucumbers in half lengthwise. Use a spoon to scoop out the seeds, creating a boat shape. Set aside.
In a mixing bowl, combine the shredded chicken, Greek yogurt, mayonnaise, celery, grapes, Dijon mustard, garlic powder, and onion powder. Mix well until all ingredients are evenly coated.
Season the chicken salad mixture with salt and pepper to taste. Adjust the seasoning as needed.
Spoon the creamy chicken salad into each cucumber boat, filling them generously.
Garnish with fresh dill or parsley if desired. Serve immediately or refrigerate for up to 30 minutes before serving for a chilled option.