Ms., I was in somewhat the same boat you are back when I was pursuing my sorority. My parents had no knowledge of sororities except for what they would see in the media (mostly negative), and there was a family friend who was telling my parents that I was joining up with a system that was historically racist, etc.
I just tried to show them the types of things we were doing in the community, but they really hated the fact that I never came home because I was always participating in sorority functions. It took awhile, but my parents came to love my sorority (they even donate now) and my sisters. My parents have even purchased paraphernalia for me, on their own!
They always ask me to bring sisters by for family functions, and have our national website bookmarked so they can read up on what types of things we are doing.
I think you should pursue the sorority of your interest, and your parents will come around.