I don't know of anyone in our town that has had a grad. party besides at their own home, can we be different!
Answers: Would we be laughed at to have it at a restaurant? What do you think?
At home you can have friends come & go without worrying how much money youre going to be spending on food for people not staying to eat it. I'd leave the restaurant for family celebration.
Do whatever you like that will be fun, affordable, and safe. In my city, the senior classes sponsor a dinner/party cruise on the river. Nobody ever makes fun of them for that.