With PHs, I would just start where you want to start. We had 2 grad nights during our trip in 2023, and I really didn’t notice much difference to any of our other trips, as far as crowds (a few loud groups on a few rides, but really no big deal). The party is at DCA, so some kids will buy the DCA-only grad night tickets, but others by the tickets that allows them in to both parks. So I would just start where you want to, and then use your hopper if it starts to get too busy at one park or another (typically DCA may start to feel busy in the evening, but again, it really didn’t seem noticeable to us; I was really worried about it, and it was no big deal). Have fun!!