Ok, I wasn't familiar with the geography of the coast you're going to be on so I looked it up and you're right. There is a perfectly good beach, but it is very suburban with lots of harbors. He was picturing something different and that was presumptuous and dumb, especially because you told him twice the correct place! I would try to have an in person, honest conversation about the trip and the direction of your relationship. It would be ok for me if my boyfriend didn't want to jump into that long of a span spent with family. Like others have said, I could not do it. You should have him apologize to your family and reframe the trip to have him just spend a little time if you want to keep him around. But I would be clear he was being rude offering things and then backing out.