I flew LHR-ORD on March 5 on a res that I booked PMUA in February. The LHR-ORD UG miles + co-pay had cleared day of ticketing, but since it was PMUA my CC was not charged at that time.

I did OLCI on March 4 T-24 and before it would proceed any further, the website made me enter my CC info to pay for the UG. Everything went fine; I gave up my CC info and I got my BP for my FC seat.

I know that your UG hasn't cleared yet so it's a little different but I wouldn't mess with the reservation, as long as everything seems to be as it should. You don't want to lose your priority on the WL. My guess would be that the worst that happens is that the website asks for your CC at OLCI, or you can't do OLCI for the segment if it hasn't cleared at the time you try to check in. If that happens, check in at the airport and they will probably ask for your credit card at that time in order to process the upgrade.