Hi Stacy,
It's easy to get from Magic Kingdom Park to The The Campsites at Disney's Fort Wilderness Resort for
Chip 'N Dale's Campfire Sing-A-Long. Simply board the resort launch for "Disney's Fort Wilderness Campground", located just outside the gates of Magic Kingdom Park, and it will take you right to the area where the sign-a-long takes place.
You can take the resort launch back to Magic Kingdom Park when you're done if you're leaving within an hour of theme park closing. Then you can board a bus back to your resort at Magic Kingdom Park. You can also take the internal shuttles at Fort Wilderness to the front of the campground and take a taxi back to your resort. For me, taking the taxi is the easiest, and least stressful, option of the two. It will allow you to relax and enjoy the campfire and movie, without worrying about making the last resort launch back to the park.
In October, I would expect the campfire to start around 8pm, so I would plan on leaving Magic Kingdom Park no later than 7pm. Be sure to check the website for updated times as your vacation gets closer.
Please let me know if you have any other questions, Stacy.
Have a magical day,
Ashley