Let them bake cake by themselves
Here’s a simple recipe for hot milk sponge cake my daughter has been making since she was four. With a little set up, the adult supervision is minimal.
Preheat oven to 350 and grease an 8-inch pan. Get out a mixing bowl and four smaller bowls. Line the four small bowls up in a row, and put the numbers 1, 2, 3, 4 under them. In the first bowl, put 2 eggs (if your child has trouble cracking eggs, put 2 cracked eggs in the bowl); in the second, put one cup sugar; in the third, put one cup of flour and 1 teaspoon baking powder, in the fourth, put 1/2 cup milk and 2 tablespoons of butter, warmed until the butter melts.
Then, follow the numbers. Have your child put the eggs in the mixing bowl and then whip them with a fork or rotary hand mixer for a couple minutes, then add the sugar and mix with a spoon. When the sugar is all mixed in, add the flour mixture, and when that is all mixed in, add the milk mixture. After mixing, pour into cake pan and cook until it passes the toothpick test (20-25 min.). If you want, sprinkle powdered sugar on top and/or serve with fresh fruit.
[Edited in 2012: When I originally posted this, I neglected to credit the original author of the hack! Big apologies, too little, too late, I'm afraid. -- Asha]
More: Hacks for birthday cake