This now sounds like a farm/ ranch installation. Have your quoting electricians show you Article 547 in the 2002 Code or the adopted code in your area.
Personally I would recomend you have 4 wires into each building served by the on pole disconnect. The on pole disconnect is your service or should be made the service. All other panels are sub panels. This will entail more work, but IMHO be the best way.
good luck.
