Thinking about making Whoopee Pies

I want to bake tomorrow and I have about 3-4 cups of cream cheese and butter cream frosting left over from making a Gooey coconut cake, I need to use it soon.

I read the Whoopee pie recipes on line. Making the chocolate cakes looks easy. I have a bag of marshmallows and could melt some and add to my frosting. I remember my mother used to add melted marshmallows to her powdered sugar frosting.

My worry is that the melted marshmallows will cause the frosting separate. I know proper temperature of each when incorporating them is going to make or break my project.

My other option is to make another coconut cake and wait until I go to the store and buy a jar of marshmallow cream because I am really wanting to make whoopee pies and don't want them to be a failure.