I'm pretty sure Ohana doesn't open until 5:30 so you would be waiting about an hour anyway.
You may have to wait some time to get a seat, and it's possible you may be told they can't accommodate you at all if the restaurant is fully booked with ADRs.
'Ohana opens at 5 for dinner, and there is always a very long line of people with the earliest ADR's checking in. If I were you, I would start lurking upstairs by the podium around 4:15 or so, and try to be the first in line when they open for check ins. Good luck!