Bake cake in a 13x9x2-inch pan according to package directions. Cool completely. Leave cake in pan and frost with chocolate frosting.
Sprinkle chocolate cookie crumbs unevenly over cake as patches of dirt, keeping some areas uncovered. In a medium bowl, stir coconut and green food coloring until until coconut is desired color. Sprinkle over cake to make patches of grass.
To make tepees, cut pretzel rods to 5-1/2 inches long; discard shorter pieces. Tie three rods together with clean kitchen string, 1 inch from their tops. Spread rods into a tripod shape and press ends into frosting on cake. Repeat with remaining rods. Cut tortillas in half. Keep one half of each tortilla, discarding remaining halves. For each tepee, place a tortilla half around a pretzel rod tripod. Secure each with a toothpick. Cut a 2-1/2-inch slit up the front of each tepee. Pull back flaps and secure each with a toothpick.
For campfire, make a small ring of candy pebbles in front of tepees. Fill circle with some of the pretzel sticks, broken to fit in circle, and strips of fruit leather to resemble a campfire.
Decorate the campsite with peanuts for pathways, remaining pretzel sticks for fencing, and rosemary sprigs for trees and bushes. Makes 24 servings.