Hong Kong Visa Or No Visa?

Hello, I am a US citizen and my wife is a Canadian citizen. We arrive into Hong Kong on 8 September 2016 at 1430 hours local time, and depart for Shanghai 11 September at 0920 hours local time. My question is: Do we need a "Hong Kong Entry Permit" or, some such document or not? ... I am being told conflicting answers. One China information website says we do not any special entry permit , and yet, the Chinese Embassy/Consulate website says that we do. ... Which is it?
Thank you,
Antonio Lopez