Okay. I will just tell my opinion. If it's not convenient for you, then let it go.
Perform something you love. That's important because if you play a music which you love, you will start to have good impressions while playing. But try to avoid extreme notes for example, Chopin's Ballade...I don't mean to discourage you but it depends on your level so you don't get mixed up or exhausted.
Also try not to play music which is so quite or relaxing like Debussy's Arabesque No. 5 because this can possibly make some people too relaxed and not focusing. Play something which attracts attention.
Also try to avoid hard musics because not all classical musics can be understood by attention. Avoid as well musics which you didn't even start with because you must work hard from now for the concert and it can perhaps take lots of time to understand and practice the new music. If Nutcracker music suits your strength and level, go for it. Tchaikovsky made many nice Nutcracker musics. If you want to perform a music which is from level 7, fine.
What matters that you work hard. And no one is perfect as we are not Vladimir Horowitz hehe.
Sorry for talking too much.
<Added>Since you are going to perform in December, pick a winter music. It can be easy or difficult but this may give nice impressions to the people.
