Did you get a resolution to your question? I would probably not frost and decorate ahead of freezing. Put a light layer of frosting on the cupcakes, that will keep them moist. Then freeze When you thaw complete your frosting and decorating. What did you end up doing, and did it work out for you?
They usually recommend not frosting cupcakes prior to freezing. Freeze them on a cookie sheet if you can then you can transfer them to a zip-loc bag to make it easier to store them. Firming them up first will keep them from damaging the other cupcakes. If you have more room or flat is better, put them in an airtight container. The more air you can remove and keep from burning the cupcakes in the freezer, the better. They will thaw quickly on the counter so you can frost them then. If you are going to freeze frosted cupcakes, I'd wrap them well in plastic wrap (again less sticky if you can freeze them on the cookie sheet first) and then wrap again in aluminum foil. The double layer will keep them from burning. Take them out when you are ready and take off the wrappings to thaw and eat.