To clarify, is your query only pulling posts tagged as the parent category and nothing tagged as a child category? And are you saying you’d like to have everything on this page?
You might try changing
cat and get rid of
But TBH you may want to try a different approach at querying; this question/answer suggests that
query_posts() is not the best method: When should you use WP_Query vs query_posts() vs get_posts()?
Another approach would be to query for the IDs of the child categories of this parent and then loop through them with individual post queries – if you’d want them in six sections.