The kids can get hands-on with this cinnamon-scented dessert recipe. Let them blend the crumble topping with their fingers until the mixture reaches the right consistency.
Preheat oven to 400 degrees F. In shallow 2-quart glass or ceramic baking dish, toss plums with lemon juice. In cup, mix cornstarch and 1/3 cup sugar; toss with plums until evenly coated.
In medium bowl, mix remaining 1/3 cup sugar with oats, flour, and cinnamon. With fingertips, blend in butter until mixture resembles coarse crumbs. Sprinkle oat topping over plum mixture.
Bake crumble 25 to 30 minutes or until plums are tender and topping is lightly browned. Cool on wire rack 10 minutes to serve warm, or cool completely to serve later. Reheat if desired.