Don't get 20's, you'll eventually try 22's and never go back. If there are no roots or rocks or anything to break your paddles then get 22x11x8 10 paddle triple buff haulers. If there is any debris get the same size 9 or 10 paddle regular or double buff xtreme's
I just re-read your post, if you're only going 2 times a year get the tires led suggested, but for sure get 22's, especially for the snow, you will have much more ground clearance