A (helicopter) mom here.
My son was accepted into a PhD program for this fall. The day he accepted the offer, back in April (the 9th, I think), the Graduate Administrator emailed back that he would be getting information about orientation, enrollment, etc., “shortly.”
He has heard nothing yet. Is that unusual? Or is it par for the course, meaning I should stop worrying (about this, anyway!)?
This is not only university specific, but department specific.
He could email and ask. My daughters graduate school department has a graduate school coordinator who she has been communicating with.
He should absolutely contact the department. Specifically the Graduate Program Director for the Department he is entering.
D is finishing her first year of a PhD program. Her department had not sent the info that you seek at this point last year. D stayed in touch with other students she had met on interview weekend, so she knew she wasn’t the only one missing that info. I think that until the department got beyond graduation they were just pretty busy. Orientation dates at minimum should be on the university calendar on the website.
It actually had not occurred to me that orientation dates would be on the calendar, but I just checked, and sure enough there it is – so now I at least know the date!
I suggested that S contact the Graduate Administrator, and S replied that he was thinking of doing that come June. I guess that’s not too far away, but my concern is that if he somehow missed an email (went to spam or trash, whatever), and everyone else has already registered for class, there will be a problem. After all, the GA said on April 9th that the information would be sent out shortly . . …
As I read what I’ve typed I cringe at what a helicopter mom I am – for an adult graduate student, no less! – but there it is. I do my best to control it, honestly! 
Thank you all for your replies.