First of all, I am somewhat offended by the comment of whether the people that work there are female. Abuse has happened from both sexes. What is important is that those that work there are screened individually, which is the case at the Mariner's Club.
Those that work there all have experience with children, one is a Kindergarten teacher by day, Mariner's Club attendant by night. The club is designed so that anyone can see what is going on inside...many times there are adults that see the ping pong table and all but beg to be let inside.
Overall, it is a very safe place...and you should feel completely safe leaving your child there while you go to CityWalk.