There is not actually any rule that the CC must match the AAdvantage account---I have used my credit card in combination with my spouse's miles (over the phone, not online). However, what you are trying to do is fraud (using miles without the account holder's approval), and that is a different matter altogether.

I don't recall if AA allows you to inherit the miles---others will know this. They might allow it even when it's not in the rules, if you ask nicely and don't try to trick them.