Hi Ashton!
Mickey's Not So Scary Halloween Party is by far my favorite event at Walt Disney World! The Boo-to-You parade and HalloWishes are both, in my opinion, the best fireworks and parade at Walt Disney World. Not to mention the trick-or-treating opportunities and the chance to meet characters that are not normally found in the parks such as The Seven Dwarfs. As its name implies that party is in no way scary, but for a two year old there might be some parts that could be a little intimidating. Chances are if your daughter is frightened by meeting the characters in the park during the day, this party might be a little too overwhelming for her age.
My children loved meeting most of the characters and seeing the parade, but were often fast asleep or very cranky long before the party was over. While I normally suggest sticking to nap and bedtime routines as much as possible on vacation, I would make sure that your little one gets a nice long nap if you choose to take her to the party. Purchasing your tickets in advance is ideal for saving money and time, but I would wait until you arrive to see how your little one is going to respond to meeting the characters. Chances are if she does not want anything to do with the characters during the day, she will most likely not want anything to do with them at Mickey's Not So Scary Halloween Party. Luckily, you will be going in September so it is unlikely that the party will sell out especially ones held on a weekday.
I absolutely recommend that everyone attends this party at least once. If your little one might not be up for it, I would save the money and put it towards another special experience. I hope this helps and please visit us again if you have anymore questions!
Best Wishes!
Mandy