Bake cookies. You will need two cookies per treat. Prepare dough and roll out dough 3/16 in. thick. Cut using largest Cut-Out from set.
Invert mini whoopie pie pan and spray with vegetable pan spray. Drape dough over every other pan cavity, pressing to smooth surface. Bake 10-14 minutes, or until firm and golden brown. Cool pan on cooling grid 10 minutes. Carefully loosen bottom edges of pan using spatula.
Fill treats. Fill shaped cookie with mini candy-coated chocolate candies.
Make piñata treats. Prepare royal icing. Tint green. Use tip 8 and green icing to pipe a line around rim of candy-filled cookie; attach second cookie. Use tip 8 and green icing to pipe an additional line around edge. Immediately roll in white nonpareils.
Decorate tree. Use tip 16 and green icing to pipe shells: seven for bottom row, five for second row, four for third row, two for fourth row and one for top row.
Immediately sprinkle with holiday nonpareils. Place star sprinkle on top of tree.