Hi Jennifer,
How adorable! I'm a huge Minnie fan, too, so I applaud your daughter's good taste in characters and costumes.
You will find character meet and greets throughout the park during
Mickey's Not-So-Scary Halloween Party. The party map you will receive at the entrance will show you all the locations.
The wait times for rides and attractions, including many of the character greetings, are usually shorter during the party than on a regular park day. I've never been on Halloween night, however, which is always a sold-out crowd and will be busier than on other party nights.
I would head straight for Minnie in the Storybook Circus section of Fantasyland as soon as you arrive to be sure you get that special picture. There's a Trick or Treat Station right next door to the Minnie greeting area, so you can start collecting candy right away as well.
The longest lines for character greeting during the party typically are for Jack Skellington and Sally, the Seven Dwarfs and some other characters who aren't often available during the rest of the year. Those may not be your picks, but I recommend prioritizing your top characters for pictures and autographs so that you can enjoy all the other aspects of the evening. Don't miss the
Mickey's Boo to You Halloween Parade or the
Happy Hallo-Wishes fireworks!
The party starts at 7 p.m., but party guests can enter the park as early as 4 p.m. I'd get there as soon as possible to enjoy every moment.
Happy Halloween to you and your Minnie,
Wilma