Setting the scene in a memoir is not an abstract endeavor. Using the techniques of fiction writing, you do not write description for description's sake. Rather, setting the scene is an aspect of the mood of your point of view character. In your memoir, it is you who are the point of view character.
But if you decide to use the scene from the picture prompt at the top of this page, you're being called to write from either the child's or the adult's point of view. If this is a happy occasion, the character will see the surrounding much differently than if something sad or trying has just happened.
Another way of saying this is: What the character sees is more important than what you as the writer want to describe. So although you may see this is a lovely bucolic scene, it could actually be one filled with dread.
What if the father is kidnapping his son? What if the child's mother is terribly sick? What if the parents are separated, and this outing is part of the father's time to see his child? What if this is a happy, wonderful moment of togetherness?
What if this is the most favorite place in the world for the child? What if there's something scary for the child? How is he sensing the mood of the adult? What if he pulls away and falls into the water? The What Ifs are endless!
Does the picture evoke a memory, perhaps a scene from your life which you haven't considered? It doesn't have to be in the woods by a body of water. It can be any place. One of the characters is you. What is your mood? See the setting through the you character's point of view.