Congrats on the babymoon.
1) I always take whatever building I get as I have no preference. Others here like to be close to the main building, however, this is a very well-laid-out resort, with no building far from the main. Your request for a King might determine your building placement.
2) I have stayed in a King room, dormer, and loved it! We had a lagoon view, looking at the Grand 1 Yacht. Sago Cay. Remember, there are only a few King rooms at GF, so your request might not be granted. But I bet if you let them know ahead of time, that you are pregnant and need lots of room for you and your pillow (hahaha), I'm sure they will try and do the best they can.
Have a wonderful time!!