The little boy is smiling as he crosses a rope on an assault course.
Some people have gone to the woods for training.
Just because the boy is on an assault course does not mean it is in the woods and that he is there for training.
A little boy is mentioned, not multiple people. An assault course does not have to be in the woods. Assault courses can be used for things (such as amusement or exercise) other than training.
People is plural and boy is singular; assault course may be indoors or outdoors so it does not necessarily mean that it is in the woods; a boy may cross a rope for many reasons other than training.