To make a really cool, relatively simple cake for your boy follow these instructions:
Bake four mini-loaf cakes using your favorite cake mix. (about 3-1/2 x 4-1/2 inches each.)
Ice each one smooth – one with red icing, one with blue icing, one with green icing, and one with yellow icing. Use the cake iced in red as the engine: Make a smokestack for the engine with 2 large marshmallows. Frost them together with green icing. Attach the marshmallows to the top of engine with a toothpick. Using green icing, attach a piece of white curly ribbon or candy on the top of the smokestack for smoke and attach two white or yellow gum drops to the front of the engine for headlights. With a spatula, place a small mound of yellow icing on top of the yellow car; add small chocolate chips to resemble coal. Place two or three small plastic cars on top of the blue car. Stick small stick candies, such as licorice pieces on top of the green car to resemble metal parts. Decorate the sides of the cars with various small hard candies for decorations. For wheels: With icing the same color as the car, attach 4 large candy discs, such as peppermint swirls, to the bottom of each car. Connect the cars with one-inch licorice whips or pretzel sticks.
Your boy and his friends will enjoy all the extra candies! Have fun!