Hello, Natalie,
No reservations necessary to stop by and sing with Chip 'n Dale! It does traditionally happen every evening, but always keep an eye on the weather which could change the event.
If you have any questions about it once you arrive at Walt Disney World, you can stop by any Guest Relations at the parks or any resort concierge desks to inquire further. You may also want to visit www.buildabettermousetrip.com and click on
Activities & Characters at the top. Once at the next page, click on
Ft. Wilderness Campfire Sing-Alongs for more helpful information.
By the way, did you know you can book a
holiday sleigh ride at Ft. Wilderness? (I linked you to an article from last year, but they are available for 2012).
Have a great trip; please let us know if we can help again.