So. Paizo, for instance, has a "community use" license which would allow you to create an "insert" for a published campaign setting as you have done with Shendenflar and provide it to people (free of charge) in the way you plan. I do not think that Wizards has anything similar so, technically, you couldn't really do that as you don't specifically have the right to use their IP...even to the extent of saying "Shendenflar is set in the World of Greyhawk between the x and the y..." In truth, however, you could probably pull it all together and post it somewhere and not sweat it until you got a C&D letter from their lawyers - *probably* never, unless they decide to re-publish Greyhawk and get all jiggy about everything.
I am not a lawyer. They might just the same decide to sue the pants off of you...so take my comments with that in mind.