In 2003 we were originally assigned to the Mansions, but was moved at check-in upon request; It was just my mom and I. Our room did have a trundle bed, but the CM didn't give us a hard time at check-in about it.
Like another poster said, I think it does depend on how full the resort is (even more so how many families of 5 are booked) and when you check-in/the CM checking you in.