I hope it's an on-site hotel so you get EE. Also, if you want to chance to not stand in the queue for too long, I'd get to the gate well before EE and sit. Then once you're in and if it's Universal for EE, to head straight to Kings Cross, go through the queue, and sit in line to wait for them to allow you to go to Hogsmeade, since that's where the Hagrid coaster will be.
OR if in the chance it is IoA for EE, I'd get to the gate an hour, or so before EE and sit in line, then when it opened, bolt towards Hogsmeade.
If I had to do the waiting, I'd rather sit for most of it, except for standing for hours. I'm sure there will be plenty of people that might be ahead still, but I think using this method will lessen the chances of waiting longer than you would, if you got there just at EE, or after EE.
Also, *knock on wood* rides are unpredictable at this period, so for all we know even after the official opening date, they might delay openings, or wait in line longer due to it being down during the day. So, if you truly want to go on that ride, you'll have to be patient.