I'm getting ready to do a cake that is going to take some building up with rice crispy.. i'm going to do Mini Mouse face and have never used rice crispy successfully with a cake. Anyone have any good ideas to help me? It's for a 1st birthday so it has to be special with no disasters!

Use a lot of butter or shortening so it doesn't stick to your hands.
Use plastic wrap to shape it. Squeeze it really tight, like squeeze it like you're trying to kill it. Make a block of RKT that's hard as a rock, then refrigerate. Then you can carve it easily.
When you make the RKT, add extra RKT that have been crushed in a blender. That makes for a smoother texture. You have to play with the recipe when you do this so it isn't too dry.
Good luck!