I went to Grad Nite a couple years ago, still got my disney cup, mickey ears, and picture frame, and god knows what else I bought, ohh and of course a t-shirt.
It's treated like any other special event, like the christmas party, night of joy, halloween party, They shoo every one out and let the seniors have a run of the parks. I know they close it about 6pm, so don't plan on watching Wishes those nights. And even though they got a bizzillion concerts and such going on, I don't think the noise should be much of a problem out at the campgrounds.
Since they're running about in the MK all night, it won't affect any hotels since they bus them in, in the afternoon and bus them out right afterwards. Crowd levels should be at normal levels.