Union membership in the CPSU

My child has joined the Federal Public Service, has been there more than 6 months and is past they're probation period. It is they're first professional job and they love it.

I work for the NSW government, I am in the NSW PSA and I think union membership is good thing to have in my situation. Before I suggest my kid join the CPSU I want to ask the people here if there is anything I should know? Is there discrimination against members for example? Does it matter what department they're in?

Thank you to everyone who makes an honest reply.