Should I Attend the Wedding of Someone Who Is into New Thought and Against Christianity?

Questions about whether to attend the wedding of someone who is into the New Thought movement and will have New Age items at the wedding location, whether one should not listen to hymns sung by Latter-day Saints, and how to respond to the Buddhist “Walk for Peace.”   Should I attend the wedding of my sister, who is into the New Thought movement and will have a meditation yurt, a drum circle, and other New Age items at the wedding location and is very outspoken against Christianity? I’ve found that Latter-day Saint singers sing hymns that I like, and I get disturbed by that. Should I not listen? How should Christians respond to the Buddhist “Walk for Peace” and the people and churches excited to see and support it?