My suggestion is similar to the ones by the earlier posters:
* Break the itinerary into two. Secure the awards for the non-status passenegers first.
* The GO passenger can be on waitlist. If not cleared a few days before departure, the GO member can use seat guarantee to purchase the ticket. Note that the member must still be GO at that time to do seat guarantee, and the seat guarantee must be done at least 72 hours (I will suggest more time just in case) before departure.