I do this almost monthly (next months trip is free on Rewards points). When the niece can't make it I get A or N for just me so I don't hear anyone thru the door and the toilet flushing.. You HAVE to call. If you have to...don't worry too much on non-adjoining. Book and keep calling back for a reassignment. They "hold" rooms, and if not paid, they are turned back in. So (I've heard this a number of times) train full...call back the next day...4 rooms opened up!
I always take 2 rubber door stops for that wall or the door, WD-40, cardboard pizza lid & duct tape (1 outta 10 ceiling vents actually close!).
Another reason to call: you can't mix points and cash on the same On-Line reservation...but no problem with a live person. And you really need to join the Rewards program as you get a special number to call where the say "Hello" and not "push 1 for this, push 2 for that" LOL Yes, if really busy you might hold for a minute, but not usually.