My DS and I did the Blue Lagoon beach day about a year and a half ago and enjoyed it. The boat ride over was lovely and the beach was not crowded at all. If you go, I would just suggest having a good breakfast and bringing some packaged snacks as the lunch that was included was not good at all. We ended up eating a late lunch on deck when we got back to the ship, which was fine.
I haven't been to the Hilton, so unfortunately, I can't comment on that.