Wire Selection for a detached shop
One thing to remember regarding voltage drop, it is heavily dependent on the actual current draw on the conductor.  When you say that you are running 100-Amp capacity to the shop that means you are running wire that can handle that much current.  That is not the figure to use to run a voltage drop calculation.
First make a list of all the items in the shop that you would like to run;  include all items that are slated to be added in the foreseeable future, be realistic, include lighting and peripherals.   Now narrow that list to those items that likely will run at the same time.  Now determine the amp draw for each of these items.  Add those loads together.  You can add a buffer factor if you'd like.  This is the number to use in a calculation for voltage drop. Happy calculating.