Is it possible for them to be having a meeting that is disintegrating at that time? I mean, they don't have to live together to be in one place at one time, do they? I go to Mythmoot once a year and I don't live with any of those people.I think it's impossible to have both families of Noldor present in the immediate vicinity of Thorondor's landing, unless they're living together in one reunited camp, which they can't be. But we can have Thorondor descend within one of the camps, and choose which will be most dramatic (Amysrevenge has a good suggestion for justifying whichever camp we want). The other camp will need to be told by Fingon or a messenger.