Viewpoint vs. Point of view
Solution 1:
In your example, a child's point of view can only be understood in one way, while a child's viewpoint could be construed as meaning "from a vantage point closer to the floor than that of an adult", so I would prefer the former.
Solution 2:
Point of view is more than three times more frequent than viewpoint in the Corpus of Contemporary American English. That shows a clear preference, particularly when you consider that some of the instances of viewpoint will doubtless be in the sense ‘a place from which you can see something’.
The preference for point of view may in part be simply because viewpoint has that other sense which point of view does not have. Those who use the latter to describe a particular way of thinking about something will not go wrong.
Solution 3:
I prefer "point of view" rather than "viewpoint", for physical and conceptual expression. These examples support usage of "point of view" in a physical, rather than conceptual context:
- Films and video games use "point of view", or the shortened form, "PoV".
- Some graphical interfaces use a "heads up display" (HUD) described in terms of point of view.
- In physics, certain problems have two solutions, depending on the "frame of reference". That is analogous to "point of view".
Despite these examples, I prefer point of view, because it is used more often, and is always understood.
Solution 4:
to make this choice as simple as possible remember this; one is a opinion <--point of view
the other is a location, a position from which one observes and reports <--view point: the mental place you choose to mentally "sit" and observe in order to respond to or write about the situation.
Solution 5:
I think you can also make an aesthetic choice on occasion. For example:
- "It is our desire to introduce people to a wide range of points of view."
- "It is our desire to introduce people to a wide range of viewpoints."
The second one sounds better because it's less cumbersome, yet still means the same.