Icing for hot weather?

When you are talking about those kinds of temperatures, there isn't really any icing that is going to hold up well. Fondant would do the best for the cake and royal icing for the decorations. All icing has er or shortening and in temperatures like that, er and shortening melt. There is no getting around it. And if you keep it in the refrigerator until they pick it up, it's going to sweat when you take it out. So what I do, is to tell the customer ahead of time what the consequences could be when the temperature and/or humidity is up. And that it is better for the cake to sweat a little bit than for it to melt. So if they could just refrigerate it up until the last possible minute would be best. If they are willing to do that then you could use er-creme or cream cheese frosting. And about the er flavor crisco; I use regular crisco and add almond extract for better flavor when I make ercreme. But I prefer the taste of cream cheese icing.