In a large bowl, mix together the sugar, butter, shortening and eggs in large bowl.
Once they're well combined, stir in flour, cream of tartar, baking soda and salt.
Pinch off about a rounded teaspoon of dough at a time, and roll them into balls.
Mix together the ¼ cup sugar and the cinnamon for rolling. Roll the balls in the cinnamon-sugar mixture until the outside is coated with a layer of cinnamon and sugar.
Place the cookie balls about 2 inches apart on an ungreased cookie sheet.
Bake the cookies for about 8 to 10 minutes.
Let the cookies cool for a couple minutes on the cookie sheet, then move them carefully to a cooling rack to finish cooling.
Recipe by Sweet Party Place at https://sweetpartyplace.com/classic-holiday-kids-cookie-favorites-snickerdoodle-cookie-recipe/