For Shanghai, I highly recommend you consider Marriott. For Hong Kong, Marriott's options are a bit overpriced imo and Hilton really only has the Conrad (and the Garden Inn, guessing it's not a contender for your vacation). The Hyatt Regency in Sha Tin seems nice and I have a friend's family that just completed an enjoyable staycation there.

I have had success getting free breakfast for a second room in a Beijing JW Marriott but the manager had to personally allow it.