I'd say it may depend on your son's interest and attention span, as well as your intentions for your day(s) at Epcot. We did Epcot at the holiday time when DD was 5. It was her first trip and we really didn't know what to expect or how to plan it. She had very little interest in viewing/touring/visiting the countries if there wasn't a Kidcot station, store or ride. The holiday themed performances caught her attention for a bit, though she didn't quite grasp the concept without Santa. We used her stroller quite a bit, she did love the Candlelight Processional but she was used to going to church. But your son may have a different temperament or interests (DD still doesn't do well with storytellers and such). I'd say be prepared to move along if he isn't interested, or maybe split up if one of you is particularly interested in a performance but your son isn't.
Enjoy your vacation!