$.fn.shuffleChildren

shuffle-children.js

(function ($) {
  $.fn.shuffleChildren = function () {
    return this.each(function () {
      var $children = $(this).children(),
          l = $children.length;
  
      // Fisher–Yates Shuffle
      // http://bost.ocks.org/mike/shuffle/
  
      // While there remain elements to shuffle
      while (l) {
        // Pick a remaining element
        var i = Math.floor(Math.random() * l--);
          
        // And swap it with the current element
        var t = $children[l];
        $children[l] = $children[i];
        $children[i] = t;
      }
      
      // Re-append
      $children.appendTo(this);
    });
  }
})(jQuery);

If the elements don't have to be well mixed, you can use one line function:

// $ele — root element
$ele.children().sort(function () { return Math.random() - 0.5; }).appendTo($ele);

The main disadvantage of this method, as I said before, is poor randomness. But it still usable if you have to continuously shuffle same elements.