Stayed at Pop last week and used a twin air mattress. we moved the table and chairs over in front of the door and put the mattress against the wall. If you don't move the table and chairs you will not have enough room. My 3 kids took turns sleeping on it so everyone got their own bed. We propped it up between the bathroom wall and bed during the day.
Our Dniece is still young enough for a "ready bed", which is a bed/sleeping bag combo (her's has the princesses on it). That fit just fine between the door and my bed. She was very cozy.
That is what I was planning on for our almost 3 year old. They say you can fit a pack and play so I did not even think it may be an issue for that ready bed to fit. I got nervous when I read that the twin air mattress did not fit. I did not think a twin was that much bigger than a ready bed.