We will be there on grad night. Not by choice, but we have had our ADR's for 5 months and it is too late to change now. My question is when does it start to get busy and is there a certain "land" that we should do first. We were going to do Fantasyland then Frontierland but should we do Tomorrowland instead?
Because the MK closes at 7pm those days, and then doesn't reopen for Grad Night until 11pm (and then is only open for Grads with special tickets), I think maybe all the kids are busy getting ready to "par-tay" all day before heading out that night instead of going during the day 
I think the crowds will be managable!!
Maybe the park will be slow that day becasue no one else will want to go to it? Or maybe that is wishful thinking. 