Seats are on hinges, they can come apart which makes it easier to pack. UPS, FedEx will pack them, no need to worry about finding a box, the shipper can do that. However, it's not cheap. When I was looking at sending the cherokee seats from Denver to PA, it was about $600 for all 4.
Call around to some of the freight companies and get some prices. Use UPS/FedEx to pack then find a cheaper shipper.
Where are the seats now, and what's the destination?