It's much tamer than the slide at Coronado Springs and Port Orleans--both Riverside and French Quarter (according to my sons!)
Have your 4 y.o. walk up the stairs (you can go with him) to see if it's something he'd like to do!
It's rare to see a really good detailed photo of the slide at the Grotto Pool because it is enlosed at the end, as previously mentioned, and it's surrounded by bushes and vines. It looks very private!