Hi all - thanks for starting this thread.
This will be my 4th summer in a row in DL in June - so obviously we think it works out pretty well. As someone who only goes once a year (not local basically) here is my advice for people concerned about Grad Nights.
But first to the person who asked about fireworks I'm pretty sure after Memorial Day all of the night shows and the parade are on the "summer" schedule - so every day and some twice a day.
The important thing to note from my perspective is that I have young kids so I am not in the parks until closing but at least some of us do stay until at least 9pm. I think if you have young kids on your trip it is quite easy to avoid the grads.
-have park hoppers - one park gets crowded, just move over! Sometimes it did seem like a ton of grads came out of nowhere.
-going early is even more important! Grads don't show up until the afternoon usually so the mornings are free from grads and locals driving in. It's also overcast which is perfect park weather IMO. It can be chilly in the evenings in June for sure!!
-think like a Grad - do the thrill rides and rides everyone loves (Pirates, Haunted Mansion) early in the day - if you're worried about the crowds in the evening do a nice dinner or have some pool time - from what I could tell Fri and Sat Grad Nights are way more crowded than the others
I know the boards fill up every year with people complaining about Grad behavior - and of course I wasn't there so I don't doubt anyone's story - but in my experience Grad Nights are not a huge deal. Some people go in worrying so much about the grads I swear they are LOOKING for bad behavior from them. I think any time there are large groups of people in the parks together you can get annoying behavior, moving around in line a bit, loudness, one person starts whispering something, then everyone does, etc. but I've seen that with plenty of non-grad groups.
For me the worst behaved people I run into at DL have NOT been grads - they are adults who push and shove and treat CMs like their servants, and take photos with flash even when they are not supposed to in dark rides. I do my very best to just ignore these people and NOT let then affect my trip. But I was happy when my DH yelled "stop flashing!" at a person who was taking a flash photo of every.single.thing. in Pirates. Luckily they did stop - I am not a fan of confrontation but that really was ruining the ride.
On that note I have read several stories on this board of people who told a CM at the end of a ride that people close to them were super loud, used flash photography, or did something else that ruined their experience and they were allowed to ride again. I'm sure this totally depends on the CM but it's something to keep in mind - especially if you waited in line a long time.
I hope everyone has a great trip. I can't wait!
It is our last night though, so hopefully we will have seen and done everything we wanted to do by them. I would imagine the day of, especially the evenings, will get INCREDIBLY crowded.
I am not sure that *I* will be able to stand and wait for that long, and have almost resigned myself to blowing off WOC because of this. We'll see, but I am not going to hold down a piece of earth for 2 hours on my only (planned) DCA day. 
