Sure. After you go through testing, security, and check-in, you'll head upstairs. To the left, there are more check-in desks. If you go to the last desk (or the one right before it), there will be a manager that can help you out. She can move people around and even print you new keys, if there's time.
Once you complete this process (it took about 15 minutes when I did it last month), you'll be able to use the
DCL app with your reconfigured staterooms assignments. There are a few consequences of changing like this, though.
1. The stateroom host won't know, so you'll have to explain it.
2. You'll still have the old keys waiting in your fish, so you'll want to have those removed by the host.
3. If moving people changes your Castaway Club status for any rooms, then you'll have to ask Guest Services to fix the rewards.
4. Your Castaway Club page will still have the original room number for everyone.
5. When you check in for your muster drill, the crew members will have the old assignments on their lists. If moving causes someone's muster station to change, then that person should go to both the old and new stations to let the crew members know what happened.
And of course, you'll have to go through Covid-19 testing with your original reservations since that happens before the change.