As a "pro" who is there about twice weekly now that school is out, this is what we do:
Me (a mid 40s woman): quick dry long capris that hit just above my ankle, t shirt, zip up lightweight hoodie or pullover hooded sweatshirt
My teen boys: athletic pants/joggers or shorts, t-shirt, lightweight hooded sweatshirts
We carry the sweatshirts in our small backpacks and need to put them on around 5pm or so.
If there is NO sun in the forecast, I might wear thin jeans. My boys will wear long pants in that instance. If there is sun, or partial sun, it can start feeling warm very quicky, thus the need for shorts or capris on those days.