If considering the YC/BC you need to know that the BC has rooms that only have two queens and no daybed. They have been known to put families with 5 in that room type and added a rollaway bed for the fifth person. Sounds OK but these rooms are already smaller than the rooms with daybeds, which are smaller than the rooms in the MK area. That would be cramped for space even if you are OK in one room all together. I would stay in the YC if planning to have 5 people in the room. Also, almost all rooms have balconies at the YC whereas many have tiny, one person standing only, balconies at the BC. The balcony does give a little more space to spread out.
MK resorts are the most appealing in atmosphere, IMO, have the monorail, castle views and quickest access to the MK (except WL). They are the most expensive, but also have the largest rooms (except WL). MK Deluxe usual resort rooms (except WL) will give you three sleeping options in the MK area that are generally 2 queens and a daybed. Bathroom layout in the GF is the best with two sinks situated outside the room with toilet and tub/shower. Both the Poly and the CR have a separate little room for the toilet, but the sinks and tub/shower are in the same room together. The Poly is a favourite resort for many people, but if a balcony is important to you, about one third of the rooms (second floors) do not have balconies. Third floor rooms have balconies and first floor rooms have patios. At the CR, garden wing second floor rooms do not have balconies, but ground floor rooms have patios. The tower rooms all have large balconies.
The Poly is a great choice and was our pick for our first WDW resort stay. It has a special appeal that no other Disney resort has, IMO. Staying here is simply magical for many many people, including us. Of your list the Poly would be our choice, no contest.
Probably NOT of interest to you, but, FWIW....
Personally, however, I would book either the GF (or the CR tower room, if the bathroom arrangement works for you) in order to ensure a balcony. The extra space of a balcony is really nice. It is an easy monorail ride or walk to the Poly if you want to go there to eat or visit. the rooms here are huge and the convenience of the monorail resorts is wonderful. The CR is not exciting to look at from the outside but the rooms in the tower all have fantastic views and the walk to the MK is a priceless advantage, IMO. Everything under one roof is really nice as well and the transportation options great (except to Epcot where you have to take two monorails to get there). The pool at the CR is plain and uninspired, so that is another huge drawback if the pool is important to you.
The GF has large rooms, great amenities, large balconies, almost all rooms have good views and a walking trail to the Poly. The pools are both good. Views of the MK and fireworks are good. The grounds are peaceful and beautiful. It is truly a beautiful place to stay.
DVC rooms often only have one real bed in a bedroom along with a pull out sofa bed and a single pull down (studios or a one bedroom). Studios have very little storage space for your stuff and floor space is limited with the sofa pulled out and the trundle bed down. Two bedrooms in DVC will get you two real beds and lots of space, but naturally cost more. Booking DVC is best done 11 months in advance and must be paid in full with almost no chance of changes or cancellation with a refund. However, the price for the space that you get is much lower than booking the resort hotel rooms. So DVC can be a really good deal for those able to live with the restrictions.
Wherever you stay, a visit to the AKL is a good idea if you have the time. Perhaps a dinner at Boma and visit the animal lookout with the kids? or even lunch at Sanaa with a table by the window?
Enjoy your trip wherever you choose to stay!
