As an update, instead of using OLCI, we checked in at a kiosk. There's a special kiosk checkin flow that allowed each of the two Plats to designate one companion to go on the upgrade standby list, and we ended up as #1-#4 on the upgrade list, checked in, all still on a single PNR. The flight is now booked 17/16 in First (?) so I guess it's academic.