Hi Courtney,
I am happy to help you consider how to make your vacation memorable. First, I have to tell you that I love the time of year that you have chosen to visit Walt Disney World. In September, the crowds will be lower than in the summer, and the weather may start to cool off a bit. If this is your Sophia's first visit, I suggest that you get her a "1st Visit" button free of charge at Guest Relations at any Walt Disney World theme park. It is fun to hear cast members and other guests alike acknowledging her first trip!
If your Sophia the First would like to meet Disney's Sofia the First, there are a couple of options. Sofia the First is currently meeting guests in the Animation Courtyard, and she also is playing with guests at the high-energy character dining experience Disney Junior Play 'n Dine at Hollywood & Vine. Both of these experiences are at Disney's Hollywood Studios. Since you are planning your trip far in advance, I suggest that you check as you get closer to the time of your vacation to see if Sofia the First is still appearing at these locations as character appearances are subject to change.
I also suggest that you visit the Disney's PhotoPass photographers while you are in the Walt Disney World theme parks. These photographers will take great photos at fabulous photo spots in the theme parks. You can even purchase
Memory Maker ahead of time to be sure that you get all of these memories. Even if you do not purchase Memory Maker, you can view the PhotoPass photos online, and Disney's PhotoPass photographers will even take photos with your camera!
Finally Courtney, relax and have a wonderful time on vacation. You will make memories that will last a lifetime, I am sure. Please do let us know if you have any further questions.