You know, I came across a similar thing that happened with me. Ultimately, things didn't work out the way I planned.
I more I segregated myself off from my family, the more they distanced themselves from me. We started to drift further apart, and they started to drift further into the haraam.
I spent a long long time thinking about it, about my obligation and responsibility, and ultimately I concluded that since Allah (swt) chose to give me the knowledge of the deen, and my family have a right to that knowledge, I could not segregate myself from them. There's also various hadith that support this notion too.
In short, whilst I acknowledge that the birthday parties, etc, are not halal in every sense, I attend to maintain the ties of kinship which is more important. And alhumdulillah, after a few months of being present (not necessarily actively involved) in family activities, it made them lower their guard toward me. Before, I was seen as the "militant strict one", but now they could see I'm still a person like them, I still like to have fun, just like them. And they started to approach me and ask questions, etc... and through this way I can insha'Allah slowly work on them to remove some of the bad habits.
I'd rather be with my family and try to guide them from doing the wrong things, than to abandon them and leave them to their destination. Islam isn't about ourselves, it's about everyone, and it may be your trial and test will be your family... to teach them.
If you give up on them, why should anyone else bother to try and guide them?