My boyfriend has recently been thrown into an argument where he must chose me or his family. What do I do?

I've been best friends with my boyfriend for 3 years and we have been dating for a year and a half. When my parents first found out they forbade me from speaking to him. I was 18 at the time and chose to walk out on my family and home to stand up for him. We've had a very passionate relationship and he's even proposed. Recently he's invited me on a trip with him to pismo beach. Just him, myself, and his cousin. The only way i could go would be to give up an internship to a local radio station, this was a big deal because it was a doorway into a career. I did because i was looking so forward to it. I also gave up 2 weeks of work at my part time job. To pay for the trip i sold all of my vynal albums. Now, weeks before we're getting ready to leave, he tells me that his grandma doesn't approve of me going so I'm just going to have to stay here and deal with it. In response to that I said that he either needs to stand up for me or never see me again. I know that sounds harsh but i've paid more than my share of dues to earn that right. I am so scared that he'll leave and I've been trying to think of a way to talk him into speaking for me to his parents. What do I do?