I believe you're talking about 2 in one double, then one child in the other double and another child in the trundle, so need one more bed for the third child, correct? If so, I would try to squeeze in a twin blow up type bed. It will be tight though. You can always put it by the AC, or in the vanity area. Then, during the day, you can stand it up, or slide it in between the bed and the wall..that will free up the floor during the day.