The main bus stop is in front of the lobby. Guest services, the game room, the gift shop, the lounge,the food court and Boatwright's restaurant are all within one building - if you exit out the front entrance to the building, through the lobby, the main bus stop will be just outside, to your right. Other than decor, I don't think there is a lot of difference between the Mansion rooms and the rooms in the Alligator Bayou section of the resort. I have only stayed in the mansions, but my understanding is that the Bayou rooms have amuch more rustic decor. But, the size and basic set-up of the rooms is the same in both areas.
I know there are a couple of Alligator Bayou buildings that are very close to the main building, thus close to the main bus stop, but I'm not sure of the building numbers, hopefully someone else can help you out on that. We stayed in the mansions, in Magnolia Terrace, which was a 5-10 minute walk to the main building. We would generally go to the foodcourt or Boatwright's for breakfast, adn then just out to the main bus stop. From what I have read, the mansions section is closed right now, but it is supposed to re-open later this year, I'm not sure if it will be open for your dates or not.
Overall, this is a beautiful resort, and I think you'll have a great time!