Hey Guys, I have a problem at work...?

I am with a group of 6 co-workers and we are on a project in Houston, Texas.. Anyways the Manager wants all of us to fly out on Fridays at 6pm.. However, this Friday, my family is holding a farewell dinner party for my Grandmother at my house.. I asked my Manager if I could take an earlier in order to be with my family.. He refused to allow me.. What are my options???