How can I cover my house with fondant or modeling chocolate without melting the royal icing?

I've designed an fun gingerbread house for a local charity event. It's a fairy house shaped like a stump with a roof and windows, etc, with fairies playing outside in the snow and decorating it for Christmas. I even bought a gorgeous bark texture stamp and was planning to use it with modeling chocolate to finish off the stump. But I've realized I have a problem. Won't the fat in the modeling chocolate and the buttercream I'd planned on attaching it with cause the royal icing to melt eventually? This house needs to last a month. Would a fondant coating do the same? I've thought of trying to do a double layer--something over the gingerbread/royal icing that wouldn't damage the icing, and then the buttercream/chocolate over that. Do you have any ideas? Last resort I could make the bark with textured royal icing, but then I don't get to use my lovely (and expensive) texture stamp. Any thoughts would be appreciated.