If I am preparing my Will, etc. and the executor and successor are in other states, how can I execute them without all of us being in one place?

The parties that you name to be the fiduciaries on documents for estate planning do not have to be present when you execute the documents.  The documents just have to be validly executed in the state in which you reside.  Double check with your attorney if there are requirements for out of state fiduciaries (some times states have extra requirements).  Good luck.