Styling Menu Items Displayed Using Shortcode

I added code to my theme’s function.php file to allow me to call a custom menu in a page:

function print_menu_shortcode($atts, $content = null) {
    extract(shortcode_atts(array( 'name' => null, ), $atts));
    return wp_nav_menu( array( 'menu' => $name, 'echo' => false ) );
}
add_shortcode('menu', 'print_menu_shortcode');

What I need now is to be able to style the parent and child pages listed there. Right now they are just a list.

Parent Page
Child 1
Child 2
Child 3
Parent Page
Child 1
Child 2

I’d like to bold the parent pages and increase their font size a bit.

Parent Page
Child 1
Child 2
Child 3
Parent Page
Child 1
Child 2

Any help?

Here’s the main page