I think if the second child is 3 or under they can be in the room with you as well. Both resorts have really big rooms but I think the rooms at the Contemporary are bigger. Plus you can walk to the MK which is a cool feature. But the theming at the Polynesian is better in my opinion. I love the tropical feel and the location of the Polynesian cannot be beat. You can hop the monorail or boat to the MK, walk to the TTC to get the monorail to Epcot and when we stayed there, the bus service to MGM and AK was great. I think the Polynesian offers more of a true vacation feel. But the Contemporary is cool, too. Depends on your taste.