adjacent-elements-wrapping.php

<?php
// Wrap two adjacent elements in a containing div using jQuery.
function pe_load_js() {
    ?>
	
	<script type='text/javascript'>
  
		jQuery(document).ready(function ($) {
    
			$("#billing_customer_age_field span input").each(function(index) {
				$(this).next("label").andSelf().wrapAll("<div class='efp-form-element-wrapper' />")
			});
      
		});
    
	</script>

	<?php
}
add_action( 'wp_footer', 'pe_load_js');