ZZ it's going to vary a lot from one college to another. There will certainly be some sort of celebration beforehand. For DS, it was a big outdoor BBQ and casual. At other schools, it could be a dressier dance-type thing.
I would book a restaurant, but with plenty of time after the ceremony. They often run late, then it takes forever to get the crowd off the field and the cars out of the parking lot.
I would be very surprised if there was assigned seating, so plan on getting there early. And bring sunblock.
At DS's graduation, there was a photographer taking pictures as each graduate was handed their diploma, then another of them holding it after they came off the stage. We got an email a couple of weeks later with a link to his website to buy them. They'll want to sell you prints, but see if there's an option to buy the digital files.
DS had to move out of his dorm the day before graduation and stay with us in a hotel the night before. He gave away or tossed a lot of big things that there was no reason to take home, like his throw rug and minifridge.
You can always ring the Dean's office to confirm the details. When is the graduation?