For a kids party I always just used a cake mix. 1/2 the kids don't even eat the cake so I don't bother spending a lot of time with it. My kids cakes were always fun but I will admit by no means did they look completely professional.
Is your DS in to sports? There are several super super easy sports cakes that you can make that only require standard or semi standard baking pans, a basic cake recipe, some frosting, easily obtained candy and a spatula and a knife.
A football is easily made by baking a cake in a 9x13. Cut the ends in a curve to shape like a football. Frost with chocolate frosting. Get several white mystery airheads candies. Slice in three pieces the long way. Place two strips on cake slightly apart Slice another airhead in 1/4 inch slices the side way. Place these across the long strips to simulate the laces.
Even easier a baseball cake. Get an oven safe metal bowl that is very round on the bottom and about 8 to 9 inches wide where the batter will stop. To make it easier to cook split the batter an put part in a regular round cake pan and layer the two pieces with the round piece on top. But this step is not necessary. Frost the cake white and then use red licorice white cut into pieces to simulate the lacing on a baseball. You could also frost with orange frosting and black licorice whip to simulate a basketball.
If he's in to snakes make cupcakes, flip upside down on a cake tray in a loosely coiled or "s" shape. Frost filling in the spaces to look like a snake - could also be used to make a caterpillar.
For a more adventurous Army themed cake I made a "camo cake" which was a basically marble cake with chocolate, dark chocolate, vanilla cake mixes blobbed into the pan together I also mixed some of the dark chocolate with the regular chocolate and some of the vanilla with the regular chocolate to get some different tones of cake. I did not run a knife through the colors just left the different shades of chocolate and vanilla to mix up as they baked. I topped with green and brown frosting and them put opposing armys of little green army men engaged in trench warfare on top. I used crushed coco puffs mixed with mini chocolate chips and plain rice cereal (coarsely crushed) as dirt. ETA - I made plain cupcakes with the left overs of the cake mixes. These went to school for the school party.
also very simple - a flag themed cake
and finally - a car themed cake - I think it was the year that speed racer was "cool"
). We got a couple plain ones and decorated them ourselves each year. Just throwing out the idea....
