We actually encountered this on one of our cruises. My wife and I were in one room and our minor kids were right next door. As luck would have it, the kids were in a different muster station. We talked with the cabin steward and he directed us to take the kids with us to our station and tell the person checking us in the reason why they were with us. No one batted an eye.
I will add this was probably 15 years ago, so things for sure could have changed.