I too did a companion upgrade for the firt time last Friday (4th year Gold Elite here!). My understanding is that companion upgrade could happen only at the gate (except for Plat companion), after all the elites are upgraded. I am not sure of the exact policies here, but this was my experience:
Travelling with my family (spouse & 3 year old, on 3 different bookings), flying AAA-DTW-BBB, AAA-DTW was on CRJ, no upgrades there, for the DTW-BBB, I approached the gate agent at DTW (not at the check-in gate). The gate agent informed I could upgrade only one, and I added my spouse to the waitlist for FC upgrade, the agent paged later on to give the upgraded seat. Spouse and 3 year old ended up sitting in FC, while I had a whole row in the back!
Try here for the P/F availability:
http://flyaow.com/classcwt.htm
Try 'Availability Tool' for R-class availaibilty.
I would suggest your companion to ckeck-in online ( ge multiple copies of the boarding pass if need be) and approach the gate agent for the particular flight you are trying to get an upgrade.
On a side note: Noticed 6 vacant FC seats, requested the flight attendant to see whether she could let us sit together, and she replied "All 3 of you sit together in the back". It appeared to me that she did not like my request and she started lecturing me on the upgrade policies, when I had to tell her that I am well aware of the policy reg. FC upgardes, and that mine was only a 'request' and NOT a 'demand'. It appeared from her behaviour later on that she didn't like seeing a 3 year old in the FC cabin. In my opinion, my kid was well behaved all through out the flight, she is not new to flying, has about 24.5K flying miles(EQMs) in her own account for 2004, and all on NW metal.
Is there any NW ploicy NOT allowing kids in the FC cabin? What else I could have done, when I have 2 FC seats and 3 of us travelling together, it being obvious that a 3 year old could not sit alone in the 'back', and when I am not dumb enough to take the FA's advice that 'all 3 of you sit in the back'!