need someone's opinion

Hi! I'm really confused on what to do. My bf invited me to his family reunion this summer we are long distance so it's a 5 hour drive from me. The reunion is at his parents brand new restaurant so I can see why he really wants me there bad to have that memory.  The problem is that is the day I registered to take my grad school exam. I can change it since I was thinking that when I take it I will be distracted that I'm not with my bf when I could have been. But on the other hand I have seen his family a lot and know them well. Is it necessary to change my schedule especially since we are only dating? What would you do? There's no way I can take the test and drive to make the reunion party. I know he's going to guilt trip me so I need to decide fast. I just hate at family things how I cling to him because no one really talks to me and I feel out of place still. So if I don't go then he can see his cousins and actually socialize more.