One dessert that's easy for the kids to make on their own but looks impressive when they bring it to share at potlucks is Pudding Pie.
Mix up instant pudding according to package directions
Pour into store-bought crust (Oreo or graham cracker)
Refrigerate for a few minutes until pudding is thickened
Spread thawed Cool-Whip on top
Store in freezer until ready to serve
Quartus was so happy when I suggested that he make it (without the big kids' help) for Thanksgiving. He picked Oreo crust with banana pudding. He kept asking to go out to the fridge/freezer in the garage to check on it.