Hi Aimee!
Anna and Elsa are hot, hot, HOT! I'm sorry to hear that there were no
FastPass+ selections available for your stay. I'm going to suggest that you keep trying, as plans can and do change, so I'd check in every once in a while and check availability. I'd check in on your phone as well as through the website, as some guests have had some different options available between the two. Also, keep in mind that standby queue is also an option, so that would still be available for you during your stay.
While there hasn't been a formal announcement whether Anna and Elsa will be appearing at Mickey's Not-So-Scary Halloween Party, I'm hopeful they will! The
Disney Parks Blog usually has the scoop on this kind of news, so I'd definitely keep an eye out there!
Have a magical vacation!
Amanda