Given the background description of some cooking related query, summarize the question into a title

I make this Sweet potato casserole for Thanksgiving, it has a streusel like topping. Usually I can bake this at the destination, but this year I need to bake at home and take. I have a baking dish that has a heat resistant plastic cover and an insulated carrier. I know that the topping will get soggy if it is tightly covered after baking. How can this be avoided?
How can I keep streusel topping from getting soggy?