Run this past your inspector as I could not get consensus in ours. A 200 amp meter base with tandem lugs on the load side. 1 feeder to 1 building and the other to the other building. Both buildings have a service entry approved main and the conductors outside the building as for a single service. 14-100 has a lot of requirements for the protection of conductors except that we have a glaring exception in that the contractor installs unprotected conductors when ever we have an overhead service. The dispute in our office is one inspectors wants OC protection on each of the 2 X 100 amp service feeders but if they were a parallel run to the same panel he doesn't. Either they are consumer service or they are private owned and follow 14-100. I am of the opinion that as long as the meter has provision to install 2 wires under 1 lug and the service cables stay outside the building till as close as possible to the main switch then you are good to go.
If you chose triplex I'd go back to the top of the pole in 200 amp wire and tap both service feeders to that. Ground at both buildings. Now if there was a building where the meter is then a single 200 amp service and a single 100 amp sub.
