First off, welcome to the DIS!
I think all of the options you have listed above are great! Of the resorts you listed, I would opt for either the YC/BC or Polynesian depending on which resort theme appeals to you most. The pool at the YC/BC is undoubtedly the best on property if the pool is important to you. These resorts are also great since they are just a walk away from all of the activity at the Boardwalk and Epcot/the Studios. If, however, you intend to spend much more time in the Magic Kingdom than Epcot/the Studios, I would go with the Polynesian. It should also be mentioned that this resort has slightly larger rooms than the YC/BC. While I am sure that your sons would enjoy the Grand Floridian, the theme there is a bit more feminine than the Poly and may not be quite as appealing to young boys. Some feel that the Contemporary theme is lacking, but I bet your sons would
love seeing the monorail run through the building and being just a walk away from the Magic Kingdom. That said, I am not a huge fan of the pool at the Contemporary and do feel that the Polynesian feels like more of an "escape." The Polynesian is often criticized for being "outdated" since it is one of the oldest resorts on property-- while it is definitely a bit dated and could use some refurbishment, we still love it exactly as it is. The castle view from the beach, volcano pool and restaurants are all fantastic. Walking along the torch lit paths at night with that view of the castle across Seven Seas Lagoon is also just so

. The easy access to the TTC is also quite convenient when you want to head to Epcot. I would not worry too much about the Polynesian cons you mentioned.
In regard to the AKL, I am certain that your boys would be ecstatic about the resort if they love animals. I would absolutely suggest your going there on a future trip with them, but would not choose it for your very first trip. The location is just not as convenient as any of the other resorts you mentioned since you must take a bus to get to any of the parks from there. Definitely grab breakfast/dinner at Boma, though, so that you can check out the beautiful resort and animals! A great alternative to the AKL for a first trip might be the Wilderness Lodge. The lobby is quite similarly designed and the WL has the added bonus of boat access to the Magic Kingdom. The rates at both resorts are the same and both are the least expensive deluxes in WDW if $ is an issue.
If $ is not an issue, I would go with either the BC/YC (I give the BC the edge since it just feels more laid back to us than the YC) or Polynesian. Check out the themes of both resorts and assess what is most important to you this trip. Monorail access? Proximity to the MK? Being able to walk/boat to Epcot/DHS/the Boardwalk? An amazing pool? A larger room? A New England vs Polynesian resort theme? My bet is that you will end up finding that the Polynesian pros outweigh the YC/BC pros-- especially since you will be there in March when the weather is not necessarily ideal to use the pool.
If $ is an issue, I say go with the WL.
You truly cannot go wrong with any of these resorts. I highly suggest checking out the FAQ threads for each of these resorts right here on the Resorts forum since they are full of great information and pictures! Please let us know what you decide.
