Well I just saw that you are "technically" a family of 5, so that already eliminates POFQ.
At CSR you could only reserve a Jr Suite, which i would suggest looking into. It gives you more room and they normally have very good bus service, but it does have multiple bus stops.
Then you have POR, CBR and the cabins and all 3 have multiple bus stops with CBR and the cabins also having an internal bus route. The cabins would definitely give you the most room, but you may have to deal with using the internal bus to get to the boat dock, depending on where your cabin is located. At either POR or CBR, I would suggest reserving a preferred category that will keep you close to everything. So the cabins are the closest to MK and the other 3 are no more then 1-2 minute difference as far as travel time between them. I will mention that CBR standard room is slightly bigger (340 sq ft vs 314) then the standard rooms at POR and CSR.
Unlike Praying Colonel, I do not think that any WDW resort is really inconvenient to get to any of the parks. I think they do a very good job moving the great number of people back and forth.