The issue of weight change is due to humidity and is influenced by many factors; Humidity of the beans to begin with, What they are stored in, how they are stored during delivery. The changes can affect quality, flavor, aging, looks, etc of the beans.
Ideally you will want the beans inspected by someone you trust before shipping. I recommend using Grainpro bags (plastic bags) inside the burlap sacks if the beans are properly dried ( if humid too high, the beans will mold). This will protect the quality of the beans during shipping and storage and increase shelf life. Air versus sea shipping depends largely on quantity you want to ship, travel time,price and access. Air is much more expensive. Remember that coffee absorbs odors so don't ship it with other spices or products with strong odors.