Since you are a family of 5, the CM's will be hesitant to allow you to stay anywhere other than the AB. The only exception is if one of your party members is under 3 and uses a pack 'n' play. Still, it's not all bad news.
You have the option of calling to request a building/area/room prior to your trip. You will want to call the resort directly 7-10 days before your arrival. Confirm your reservation and make your requests then. When checking in at the main desk, be sure to remind the CM of your request. Though they cannot guarantee that your request will be granted, I understand that Disney does it's best to accomodate guest requests.
Your best bet is to request AB building #14. It is very close to the main building with the food court/lobby/etc. It is also close to the bus stop at the front of the resort. This stop is the first to pick up at POR (though it stops to pick up at FQ beforehand), so you are more likely to get seating on the bus at this stop (versus the 3 other stops around the perimeter of the resort). Building #14 is also close to the bridge to Ol' Man Island (the main pool). Since it is an AB room, it will be more quiet than the mansion rooms.
Some drawbacks of the AB rooms is that the decor tends to me more "rustic" than the mansion rooms. Still, the rooms are comparably sized when compared to mansion rooms. Additionally, there are no elevators in the AB buildings, so you may want to request a 1st floor room if you plan on lugging around a tired baby/toddler/preschooler and stroller. Again, however, Disney will only guarantee 1st floor rooms to guests with medical conditions that render them necessary (eg- guests in wheelchairs).
One last thing: if your family is celebrating something specific (someone's birthday/graduation/recovery from illness/etc)aq, be sure to mention that when making your room requests. CM's may put a little extra effort into accomodating you for a special occasion.
Hope this helps!
I don't think you will be disappointed. 
