Book the extra night. Later call guest services and have them combined
The theory is if the entire reservation isn't available new you can't make the change. Why should you be able to make a booking not. Available to other guests
Too many guests play games
I did book the night as a separate reservation. I just didn't want to have to check out and switch rooms. The inconvenience of that almost made me not book the extra day.
We requested to remain in the same room but there is no guarantee. I will call as it gets closer and ask if they will be willing to combine the two reservations