Please avoid any park that has an EMH, it makes a big difference to the crowd levels.
We accidentally hit MK at 9.30 pm to watch the fireworks on our last night and it was a late opening evening. It was bedlam, 90 minute queue just to go on Buzz. All through our holidays we avoided these days like the plague and went on the recommended quieter days, lines were minimal/non existent when entering parks at opening times. Universal/IoA opened at least 20 minutes before the official opening times.
We were expecting massive lines this time as we usually go in Feb when it is quieter but surprisingly they were extremely low if in the early hours of the day.