I did this recently at a property where I "always" get upgraded (LM Montreal).. saw the day prior they upgraded me to a Junior Suite w/ king.. nice.. but I checked in late and they were at full capacity (AKA sold my upgraded room) and they bumped me back to original booking. There was a marked difference in the quality of the room and I was cranky for having to sleep on a dorm style double bed.. but it was my own fault for booking the lower room to save a few bucks for my company..

However, if I was in your shoes I'd book the single beds and write in comments/email the property a couple days in advance to get a preferable room assignment. I guess I'm just a risktaker like that