As a Diamond, there is no premium check in on the family side, but you have access to the premium pools and premium beach.

As a Diamond I was refused even one level upgrade, but they put me in the back of building 7 (supposedly garden view) that has garden AND some beach view, so I was happy with that. They said that it was a premium room, and that was an upgrade, but I am not sure what was premium about it, but I was glad about the view and high floor.