He'll really enjoy Garden Grill, not so sure about Candlelight. If he can happily sit thru a church service, then he'll be fine with Candlelight, otherwise he may get bored listening to the narrator and the choirs. JMHO
Our DS was a couple of days shy of 3 when we went. He did okay through the first half but then got antsy. My DH was kind enough to take him out of the theater because he knew how much I really wanted to see it. So our DS did about as well as you could expect a child of that age to do.