Create separate reservations for both of you on CO.com.
Then call CO.com tech support, have them pick up your companion record
and adjust it to the $99 companion ticket (rebooked in Q I think).
Both tickets can then be paid for with whatever cc or means you decide.
You can then send in the Prestige Pack voucher, or take it to your airport
so the ticket will be finalized and you are done.

FYI - CO.com said you will get 2 1,000 bonus miles if you booked the reservations separately, separate PNR numbers and EQM miles at 100% since they are .com reservations - fully mileage on the $99 companion ticket as well.