var biggestHeight = 0;
// Loop through elements children to find & set the biggest height
$(".container *").each(function(){
 // If this elements height is bigger than the biggestHeight
 if ($(this).height() > biggestHeight ) {
   // Set the biggestHeight to this Height
   biggestHeight = $(this).height();
 }
});

// Set the container height
$(".container").height(biggestHeight);

<div class="autoheight" style="background: blue">
    <div style="position: absolute; width: 33.3%; background: red">
    Only
        <div style="background: green">
        First level elements are measured as expected
        </div>
    </div>
    <div style="float:left; width: 33.3%; background: red">
    One Two Three Four Five Six Seven Eight Night Ten
    </div>
    <div style="float:left; width: 33.3%; background: red">
    One Two Three Four Five Six
    </div>
</div>

<script>
function processAutoheight()
{
    var maxHeight = 0;

    // This will check first level children ONLY as intended.
    $(".autoheight > *").each(function(){

        height = $(this).outerHeight(true); // outerHeight will add padding and margin to height total
        if (height > maxHeight ) {
            maxHeight = height;
        }
    });

    $(".autoheight").height(maxHeight);
}

// Recalculate under any condition that the viewport dimension has changed
$(document).ready(function() {

    $(window).resize(function() { processAutoheight(); });

    // BOTH were required to work on any device "document" and "window".
    // I don't know if newer jQuery versions fixed this issue for any device.
    $(document).resize(function() { processAutoheight(); });

    // First processing when document is ready
    processAutoheight();
});
</script>

/**
 * Sets the height of a container to its maximum height of its children. This
 * method is required in case
 *
 * @param selector jQuery selector
 */
function setHeightByChildrenHeight(selector)
{
    $(selector).each(function()
    {
        var height = 0;

        $(this).children("*").each(function()
        {
            height = Math.max(height, $(this).height());
        });

        $(this).height(height);
    });
};

<div class="container">
    <div class="faq-cards">
      <div class="faq-cards__card">Im A Card</div>
      <div class="faq-cards__card">Im A Card</div>
      <div class="faq-cards__card">Im A Card</div>
      <div class="faq-cards__card">Im A Card</div>
      <div class="faq-cards__card">Im A Card</div>
      <div class="faq-cards__card">Im A Card</div>
      <div class="faq-cards__card">Im A Card</div>
    </div>
</div>

.container {
 height:auto;
 width: 1280px;
 margin:auto;
 background: #CCC;
}
.faq-cards {
 display:flex;
 flex-wrap:wrap;
 justify-content: center;
 position:relative;
 bottom:40px;
 height:auto;
}
.faq-cards__card {
  margin:10px;
  position:relative;
  width:225px;
  background: beige;
  height: 100px;
  padding:10px;
  text-align: center;
}

$(".container").height($(document).height());