It could be a club the diplomatic corps’ kids prefer. Only seeing dark hair in the rubbernecking crowd outside, so maybe it’s mostly the kids of rich Turks.
Yes, an upscale club with Turks and probably some foreigners just out celebrating the New Year. ISIS or an associated group likely doing the terrorist act since mixed sex nightclubs are “Haram” - Acts that are haram are typically prohibited in the religious texts of the Quran and the Sunnah. The category of haram is the highest status of prohibition.