How to tell parents about going to the GSA at my school

So school is starting in a couple days and I was hoping to go to the Gay Straight Alliance club or GSA for short this year. Last year I saw it and really wanted to go to it but I was very much in the closet and I saw everyone making fun of it making me not want to go. This year I am out and could care less what other people think. But I know my parents will be really weirded out and will not understand why I am going. They are also religious so they don't want me hanging out with "sinners". I also will NOT tell them I am gay that is not an option for me I can't and refuse to tell them for a long time. I am ok with lying to them but I don't know how to go to the GSA and where to tell them I am going. I have thought of telling them I am going to tutorials every Wednesday but Im afraid they will start to get suspicious of me going every Wednesday. I guess my question is, What am I supposed to tell me parents every Wednesday. I really hope to go this year so any advice would be very appreciated. :rolle: