Originally Posted by mvoight

The policy is the elite bag allowance only applies to passengers on the same PNR.
If you split the PNR, you would no longer be on the same PNR as they are, so the elite baggage allowance would not apply to them, though it is possible an agent might ignore this.
That said, as PLT, you can check 2 bags for each passenger on your PNR, so if each passenger only had one bag, then you could simply check their bags as yours and your dad's