How to provide meta_key array to wp_query?

The WP_Query() custom field (i.e. meta) query can handle arrays for field values. You just need to add the compare key to your array:

$args = array(
          'numberposts' => -1,
          'post_type' => 'post',
          'meta_query' => array (
            array (
              'key' => 'my_key',
              'value' => 'target_value',
                          'compare' => 'IN'
            )
          ) );      

        $new_query = new WP_Query( $args );