Lones,
I have never encountered a situation where they have refused a TIW card becasue the person paying was not the card holder nor have I ever seen a CM ask for ID to verify that the individual on the card is at the table, so I don't think it would be a problem if the 2nd card was issued to your mom, but you used it. Also, it could not forsee an issue if you got the original card and your dad was the one paying.