dismom3----- I really don't know if a air mattress would fit or not. I have been at POR with five. It was a little tight, but doable.(we had the trudle) The standard rooms at POR are 314 sq ft. The standard rooms at AKL are 344 sq ft. According to guide books, some standards have a queen and bunks at AKL. I would certainly ask if the three year old could be in the room. You might be surprised by the answer. I understand about 5 as we are a family of five. Disney seems to have fewer choices for families larger than four. Hope the sq ft info is helpful to you.
