There should be plenty of availability for paid upgrades on your flight, as availability in CW is J9 C9 D8 R7 I4.

However, if you are restricting yourself to taking a POUG if offered, then AIUI you either have to take the offer for both people in the booking or not at all. If you are concerned that a POUG might only be offered for one person, I don't think that this need to worry you.

If on the other hand, you want to upgrade only one person in a booking for two, you have to call to split the booking into two. But doing that will probably kill any POUG that was being offered at the time that the booking is split.