When our daughter graduated from HS, her graduation was at University of Houston. Their facility was smaller so each grad only got 6 tickets. So not enough! We were able to get some tickets from other graduates who were not going to use all their tickets. I would contact the school and find out what their policy on seating is.
We didn't have that issue when our son graduated. They had a much bigger facility, hello Reliant! =)
When the kids graduated from hs and daughter from college, we didn't send out "save the date". I sent the invites out around Easter or a little before with their "senior photo". Plus, I had told everyone before when the date was.
Our son "should" graduate from college December of 2015. I have already told my brother the date. Long story there.
Congratulations. It moves really fast after the holidays!!