Rice Krispie treats should be one of the easiest goodies to ship. I would suggest cutting them into squares first, then leave the cut "sheet" of squares together. Wrap the whole thing very well in plastic wrap then in aluminum foil. Seal in a box and put that box into another box and ship. I used to ship cookies overseas this way and never had a problem with the cookies breaking, etc.
"As a girl I had zero interest in the stove." - Julia Child
This is real inspiration. Look what Julia became!