My niece will be bat mitzvahed in a Reform Shul. I have arranged with the rabbi to live in the shul for Shabbat, avoiding travelling. BUT, the reception is Saturday afternoon and is a 15 minute drive away. If I know that gentiles are going to drive there, may I sit it their car? I would hate to hurt my niece; too many men in her family have died including my father, her grandfather. I understand that I will probably have to spend most of the party out in the hall but it would mean a lot to me to be there. Thank you

Halacha prohibits attending services at a Reform Temple- it is not a halachic shul- even if no desecration of the Shabbat were involved. I recognize that this may be a difficult halacha for you to observe, but try to find an acceptable alternative or a reasonable excuse so as not to insult your relatives.