Hi there Sabrina,
You are so incredibly welcome! I'm having a blast helping you!
The
Candlelight Processional at Epcot is such an amazing performance. The show is held in the American Gardens Theatre with performances at 5 p.m., 6:45 p.m. & 8:15 p.m. and lasts roughly 40 minutes.
The Holiday festivities at Epcot have changed over the past couple of years in which they discontinued some things. I did some research to try to confirm whether or not they will hold the tree lighting ceremony this year. None of the Cast Members I spoke with were able to confirm anything and suggested that I check again around Thanksgiving to see if their schedules were updated. You are welcome to check back with me during that time and I'd be happy to check again for you.
For the sake of this answer we will ASSUME that they are holding it this year (again - I can't get confirmation either way right now). So if you attend a 5:00 p.m. performance (lasting approx 40 minutes) and it takes a few minutes for Guests to exit the theater (depending on where you're sitting, you may not be able to immediately get out), I think you would have a hard time making it over to the tree lighting ceremony at 6 p.m. If both options are available, you'll need to choose between the two or shoot for a later performance of the Candlelight Processional.
Please feel free to check back again in a few weeks. I'm super happy to try to find out more info. Wishing you many magical memories :-) Allison