While I can see very easily how Cermony and the Faerie Method Enchantment fit together non-mechanically, I'm not sure what the intent is mechanically. Sure, all the assistants must sing/dance/whatever as well. The bonus from Ceremony should go to the second roll, the one with the Method and Power. What about the prior performance rolls? Do they all make performance rolls? If so, how do we interpret so many rolls. I'm guessing it's best to just use the leader's scores for the performance without either a bonus or penalty, but I bet there are other interpretations and I certainly may have missed something.
By the RAW, as you point out, the bonus from the helpers affects only the Method+Power roll. The helpers all have to sing/dance/whatever, but how well they do it does not affect, mechanically, the results of the magic.
Really thei could contribute with their Characteristic for the Method aplied, Presence? It isn't?
That's what I recall, yes - the helpers are basically in the background, chanting and holding candles. They're basically a background bonus that the main person adds to their roll - like having a high-quality Summoning Circle and Alter, in the Ceremonial Casting rules in HoH:S.