Ordering Subcategories

I have never used the plugin you found but it looks pretty heavy, at least on the backend, and may be overkill unless you need a lot more functionality than described in the question.

get_categories operates from cached data so my thought was to simple alter the returned array rather than perform another query or a more complicated one.

function move_cat_to_top_wpse_107314($move, $cats = array()) {
  if (empty($move) || empty($cats)) {
    return false;
  }
  $cat = array_search($move,wp_list_pluck($cats,'slug'));
  if (false !== $cat) {
    $tmp = $cats[$cat];
    unset($cats[$cat]);
    array_unshift($cats,$tmp);
  }
  return $cats;
}

$parent = get_cat_ID('aciform');
$children = get_categories( 
  array( 
    'child_of' => $parent,
    'orderby' => 'date',
    'order' => 'asc',
  )
);
// var_dump($children);
var_dump(move_cat_to_top_wpse_107314('sub', $children));

The move_cat_to_top_wpse_107314 function is all you need. The rest illustrates usage and works with data on my sandbox site.

Also, please don’t use query_posts.