A thought on Languages in Greyhawk
Lenya: Common and Rhopan
Lylamwyn: Common, Draconic, Elven, Orc, Slyvan
Belaver: Common, Druidic
Kerwyn: Common, Draconic, Orc
Raner: Common, Dwarven, Goblin
Craven: Common
Toriah: Common, Elven
Common is a modern day derivative of two languages, Ancient Baklunish and Old Oeridian.
Kerwyn probably wouldn't speak Orcish (unless there is some reason you have not yet added to his background). Instead he would know Ancient Suloise, the language of his ancestors. Ancient Suel is essentially the equivalent of Latin, i.e. Kerwin would have heard it in Church and his parents know it as Suel Wizards.
If Craven knew another language, it would be Velondi, an old Oeridian tribal tongue spoken in the Veluna-Furyondy area (including Hommlet).
Lylamwyn probably wouldn't speak orcish, instead he would probably speak gnomish or one of the "ancient human languages" (ancient Baklunish, Old Oeridian, Ancient Suloise, or Flan).