Adding an orderby filter, casting postmeta with multiple keys

Got the idea from this post to change my query : How to “orderby” the first array in a meta_query that uses multiply keys?

I moved the state query into the larger array of queries, freeing the ‘meta_key’ value to be assigned to event date

$args = array(
    'post_type' => 'tf_events',         
    'meta_query' => array( $relation, $date_query, $date_query2, $state_query ),
    'posts_per_page' => $limit, 
    'meta_key' => 'tf_events_startdate',
    'tax_query' => array( 'relation' => 'AND', $type_query, $host_query ),              
    'order' => 'ASC'
    );

add_filter( 'posts_orderby', 'my_posts_orderby_date', 10, 2 );
    function my_posts_orderby_date( $orderby, $query ) {
        global $wpdb;  
        return " CAST( $wpdb->postmeta.meta_value AS DATE ) " . $query->get( 'order' );
    }