Hard decision

I joined some meet up.groups last year.  I really enjoy the Day trip group I belong to.  I was in DC this past Sat.  My next meet up event is on Sept 14th.  I didn't look at the Jewish calendar, it's Yom Kippur, one of the holiest days in the calendar.  I am not overly religious,but I do follow certain traditions.  
I'm trying to search my heart and conscience and decide if I should follow the traditions or break with tradition this year and go on the trip.  It's to Mt Vernon.