The PCL program is set up so each booking will have a CC registered in the name of guest owner. Makes sense for liability of that booking. What doesn’t make sense, is that you can’t prepurchase using whatever CC you want for onboard services.
We have mostly waited till OB to purchase spa treatments, as they have sales OB.
If you go with the other guests all together to GS, you can switch over all cabins to your CC, if you want.
I have called into shore excursions, as was suggested, and booked us all, using my CC precruise.