When we were there on a grad night and the morning was pretty quiet at DL. If you are at rope drop you'll have time to do a fair number of rides. The grads start arriving around midday and it gradually becomes more crowded during the afternoon and evening. Tomorrowland and the thrill rides in other areas of the park (e.g. Splash, Indy, Big Thunder) tend to get very crowded so if any of these are in your plans do them in the morning.
If you have hoppers you could do DL in the morning, then head over to DCA in the afternoon. Not as many grads are in DCA during the day since they'll have the park to themselves during the grad night hours.