I've stayed at this hotel several times, and I can vouch for the fact that they do have "real" king beds.
Book your reservation in a category that says two twins convert into a king. In remarks, put "king bed." Even if it is a room where they've converted two into one, I guarantee you'll never know.
And for what it's worth, the Sheraton Diana Majestic, while nice, is a notch or two below the Palace.