Wash and thoroughly dry the grapes. Cut each grape in half crosswise so they don't roll off your fork. Core both apples and cut into 1/2-inch dice. Do not peel - the skin adds color and texture. Toss the diced apples with a squeeze of lemon juice if not dressing immediately to prevent browning.

In a medium bowl, beat the softened cream cheese with a fork until completely smooth and no lumps remain. Add the sour cream, powdered sugar, cinnamon, and vanilla. Whisk vigorously until the mixture is light, fluffy, and well combined. It should coat the back of a spoon but still pour easily.

In a large serving bowl, combine the halved grapes, diced apples, and sliced celery. Scrape the dressing over the fruit and fold gently with a rubber spatula until every piece is evenly coated but not drowning. The dressing should cling lightly rather than pool at the bottom.

Fold in most of the toasted pecans, reserving a handful for the top. Sprinkle with the remaining pecans and a light dusting of cinnamon. Serve immediately for maximum crunch, or refrigerate up to 2 hours if you prefer it chilled.