But using replace-by-fee can be of low fee, instead of using child-pay-for-parent.
If you are buying items on online stores, you can use child-pay-for-parent because the transaction would be replaced with new txid. But I have used RBF to increase the fee while sending to centralized exchanges and while sending to friends without any complain. If not necessary to use CPFP, it is better you use a wallet that is supporting RBF and use it instead to pump the fee for a lower transaction fee.
I think base on my understanding of the entire question it is only CPFP that would work out. The question is actually about C address bumping the transaction, C is the last Recipient address from the question and can use the CPFP method to bump the transaction from the remaining two unconfirmed transactions.
The only address that can actually use RBF is address A because it remains the original sender of the coins. B to C transaction is CPFP and yet to confirm so B also cannot use RBF. So C address can not use RBF because it is the receiver address