Oh come on, boxed mix is fine and anyone who says otherwise has never watched me try to bake from scratch. Last time I made a "homemade" cake it came out looking like a deflated football and tasted about the same, so trust me, the box is doing everyone a favor. The frosting is where you can really show off anyway, and honestly most people at a birthday party just want cake in their face, not a baking contest. Do the box, make the frosting from scratch, and nobody will even ask.