In the case presented in the first post in the thread, I'd list all three individuals for two reasons. First, all three are owners of the account and FinCEN has said that you may (not must) list all joint owners for a reportable cash withdrawal. Second, because this isn't just about who's getting the cash. It's also about on whose behalf the transaction is completed. Mom is invested in distributing the funds to her kids, so she's a person on whose behalf the transaction was completed.
As for box 32 or 34, if a check is involved, check box 32.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8