I reckon Ironforge is older because it was formed at the sametime with Gnomeregan when the gnomes and dwarves started existing after the curse of flesh, they migrated from the north to find a place to live and settled in Dun Morogh. The curse was created way before lich king and even before humans even existed since humans are actually deformed vrykuls (vrykuls also victims of the curse but chose not to migrate) who were exiled and travelled to EK.
Lordaeron cant be the oldest considering Lordaeron was named after a hero of the troll wars but its location might have been established already within the kingdom of Arathi… so the location might be the oldest human city in the world, just named as lordaeron it isnt. semantics i know.
But it absolutely isnt the youngest. Stormwind is… atleast out of the humans. Orgrimmar is probably the youngest locationwise included while thunder bluff might be the oldest considering Darnassus didnt exist before the Sundering however tauren used to be a nomadic race due to how dangerous it was to settle in one place for long, eventually it became safe and TB was founded. Not sure of the exact timeline there, gotta re-read the Chronicles.