I solved the crushing problem a long time ago. Whenever I get a take-out pizza, I save the little plastic thingies they use to keep the lid of the box from smashing the pizza when you stack them 10 high in the delivery vehicle.
Life is much more manageable when thought of as a scavenger hunt as opposed to a surprise party - Jimmy Buffett
I would mail them unfrosted with a container of frosting, a container of chopped walnuts, a plastic knife and a set of detailed instructions on how to frost them. If the person you are sending them to does not have a sense of humor they do not deserve cupcakes!