Just as a data point, I was also able to go through the online check-in tonight for my wife and myself. I did have a couple times where hitting the submit button gave me blank screen that never refreshed, but going back and resubmitting worked. I didn’t arrange any excursions but did order a tray of strawberries.
Possibly other data point, I am also a Crown & Anchor member with an existing RCCL account that this reservation is attached to.