This recipe is great! You will need a large bowl, 1 cup of flour, 2 cups of oatmeal, and 1 cup of water. Have your children mix the dry ingredients first with their hands, then add water. Keep mixing until all ingredients form a large ball of dough. It will be sticky at first but keep mixing. You can then roll out the dough and use cookie cutters to make shapes, letters, or numbers. The dough will harden after a few hours.
You can also use liquid food coloring to add some color to the dough. After using the cookie cutters, push a straw through the top to make an ornament, or once the dough dries you can have your children paint them.