I think as he gets older and into more advanced reading, this can become a problem. Errors which are no worry now may become pronounced later, and lead to significant misunderstandings. You can pack a lot of nuance into small amounts of syntax. For instance, this Supreme Court case over a comma: http://www.businessinsider.com/the-comma-in-the-second-amendment-2013-8

Big-picture thinkers can use some help developing attention to detail, and I think the sooner, the better.