So I emailed the pictures to the folks at the sea slug forum... They responded with in a couple of hours and were super excited to pass them around for an ID. The verdict is:
"lamellarid snail"
"This is not an opisthobranch, it a lamellarid snail, with an internal shell , they are often confused with sea slugs, but they have characteristic tentacles. I don't know what species it is, but if you type "Lamellaria" in google and search for images you will get many similar things.
All the best!"
They believe him to be reef safe.
~matt