1. There are two places in the campground to catch buses that travel outside the campground: The Settlement bus stop-this is where you can catch a bus to AK, Epcot, the waterparks, and Downtown Disney. Depending on what cabin loop you get, it's probably about 1/3 of a mile from the cabins to the Settlement bus stop. The other external bus stop is the Outpost. This is where you catch the bus to Disney/MGM Studios. It is probably about 2/3 of a mile from the cabin loops.
2. The internal buses come around quite frequently. I doubt that you would ever have to wait more than 15-20 minutes for one (it's all a matter of timing). If you are going to the MK, you can exit at the Outpost, and walk to the dock (just a short stroll), and take the boat to the MK.
The bus transportation at FW is really not any slower than at the All Stars. In fact, depending on where your room is located, I would say that you could have a longer walk to a bus stop at the All Stars than you would from your cabin. The bus stops are well lighted and covered. There are benches to sit on while you are waiting. I would not worry one bit about waiting in the dark.
Bottom line-buses should not be an issue when deciding between a cabin and a family suite.
TCD