I think that is a great reservation time to have because this is, after all, a bar. Even though park hours end at 8pm, the rides etc do not close promptly at 8pm. You can hop in a ride line at 7.55 pm and the ride will stay open until all the queue goes through. Just make sure that you are in the park before 8 pm and in a ride queue before 8 pm.
I think Oga’s has a better, more lively atmosphere in the evenings.