Overriding shortcode defined in WordPress parent theme is pretty easy.
Just use a after_theme_setup section in functions.php of the child theme;
example:
add_action( 'after_setup_theme', 'my_child_theme_setup' );
function my_child_theme_setup() {
remove_shortcode( 'your_shortcode' );
add_shortcode( 'your_shortcode', 'my_shortcode_function' );
}
function my_shortcode_function( $atts, $content = null ) {
extract(shortcode_atts(array(
), $atts));
$out = 'content">'.do_shortcode($content).'</div>';
return $out;
}
