Excess baggage to Chicago, Illinois

My husband & I will be finishing our twenty-seven months of Peace Corps service in Tanzania in early November of this year. As we are planning to travel a little before we return to the U.S., we would like to send our 2 duffel-bag suitcases back home earlier. The dimensions of each one are: L=2.5 feet, W= 1.5 feet, H= 1foot. Weight for each one could be anywhere from 30-50 pounds. What is the cheapest/safest way to send them to the USA? by air? Could you give us an approximation of the costs for transport?? Salama, Pat & Glen, PCVs in TZ