Dear Annie: Do I have to use my only vacation on my dad’s birthday party?

Dear Annie: My dad is turning 73 next month, and my mom is throwing this big party for him. She is begging me to come, but my parents live across the country -- a six-hour plane ride. I work full time and have two kids under 5. My family only takes a trip like this once or twice a year, and if I’m really honest with myself, I don’t want to spend it on this family party.