The small plaza infront of the fountains opens at 9am. There will be a goldpass check gate to the right of the fountains only admitting those with pass's back to the DB/Beast ERT. Just flash your pass and you are in. You can easily get DB and Beast in that first hour (9am-10am) Then I highly suggest getting over to Firehawk as fast as you can at 10am when the remaining attractions open. Hit Flight of Fear while your over there.
Nickelodeon Universe has low crowds when it's dark out and its getting later in the day.