I am not an expert. But Pages and categories are two different things. You can’t move posts from a category to a page. A page is something where your write. A category is something where you file in as “categorised” in that section.
I hope I have understood your requirement correctly
Since you are using the Twenty Ten theme, you can use the Custom Menu to create a navigation tab leading to the Halloween Haunt category. Each time you post to that category, it will also appear on that dynamically created page.