Should I have a gender reveal party

My parents don't want to come because they don't want to know if it's a boy or girl. My younger, pregnant sister said she would attend back in March. I planned the whole thing around her because she works crazy hours. Now I find out she won't be coming because she "accidentally" made plans recently with my parents. I have been wanting to have this party for months now...and now my own family doesn't want to attend. My in laws will be there...but it's just embarrassing to throw a party and not have anyone from your own family there. (Of course they are all attending my sister's 2nd baby shower in 2 weeks though)