Hi there Sara! Welcome back to planDisney with another great question.
You are correct; there is a special ticketed event,
Disney After Hours at Magic Kingdom Park taking place on January 9 and other select nights through March 27, 2023. This event takes place
after regular park hours from 10:00 pm to 1:00 am.
Operating hours for Magic Kingdom Park are currently listed as 9:00 am to 10:00 pm every day in the month of January, including January 9. The Disney After Hours event will not shorten park hours for regular day Guests.
Disney Enchantment fireworks will be held daily at 8:15 pm in the month of January, weather permitting. You won't need to worry about missing fireworks due to Disney After Hours.
While most of the holiday entertainment and activities will be ending at the end of December, usually the parks are still decorated through the first weekend in January. Hopefully, you'll be able to see some of the beautiful holiday decor during your visit.
Sara, I hope I have been able to put your mind at ease. I think your plan to visit Magic Kingdom Park on January 9 sounds great! If you have any additional questions, please do not hesitate to stop by and see us here at planDisney again. Have a wonderful vacation!
Anne Marie