@SandraIRAQ,
You can stay in the same hotel but in a different room. They do have more than one room, yanno. And I imagine things weren't so dangerous when you booked the vacation, right? Those things have not changed. The only difference is that you are not staying with the dude.
As for what to do, sheesh, it's
Hawaii. Google "Hawaiian tourism" and start reading. If nothing else, bask in the sun and read trashy novels. Or send me your ticket and I will be more than happy to not only go in your stead but I will even tell off your ex if you like.