You can get the orb off the giant by gliding down and taking it, he won't wake up...
Did the eventide last night, took 3 tries....was a blast.
I figured there was a way to get it from him before he woke up, but my attempts never worked, so I just fought him to the death. AFTER I finished the island, I looked up a few tricks and saw that you could do what you suggested. That sure would have been easier, but I'm trying not to use any guides if possible.
Yeah, the island was super fun regardless of the method used to finish it.