I think given the choices, I'd go with Long-Distance Toll and not modify the Numbering Plan/Toll Strings; understanding that they'll have to dial the Access Code for all LD calls.
So it is my understanding that I'd want Forced, Non-Validated, Long-Distance Toll...
I would add the extensions to that list under Account Codes, and also confirm that the Account Code Type in their System > Device and Feature Codes > Phones profile is "Forced - Long-Distance Toll Call"
However, this does not prompt for an account code after a LD call is placed from a set with these settings assigned.
Is there something else that I'm missing?
edit: Additionally, In System > Phone-Related Information > Account Codes > Forced, I see a Folder for "Non-Validated", a folder for "Validated", and what looks like a bullet-point with "001" underneath both folders.