We just got back last week and boy, are you in for a treat of a trip! 🙂
With regards to sizing of parka, go with your usual size. The parkas take into consideration room for layers. When you get settled and are heading across the drake, I suggest heading down to the mud room with your intended layers and try on the parka and boots for sizing, and let them know if you need to size up/down. We had to size up one of the parkas and this was easily remedied. For boots, if you're a half size, I recommend going up to the next full size.
