You can use two 4-serving-size packages of raspberry-flavored gelatin instead of one 8-serving-size package. Or replace the sugar-free raspberry gelatin with regular raspberry-flavored gelatin.
If you are serving a smaller group, you can easily cut this recipe in half. Bake cake as directed on package for two 9-inch loaf pans and freeze one cake for later. Use half the ingredients, and layer them in a 1 1/2-quart serving bowl.