I love that you share your parents with us. It is obvious there is much love there. I was thinking that there was maybe 36 pieces per bench. You and your parents did a fabulous job. Looking forward to your next build.
Comment for those wondering about the galvanised hardware: I tested some differently treated hardware for an oak bench I was building last year. Oak + iron + weather is generally bad, but apart from the one untreated screw (which rusted within a day), everything was fine. So I'm fairly sure your hardware will be good. Looks like a fun build, together with your folks.