Menu – child and grandchild

Kinda new at wp and trying to hard code different menus to different pages in my site by using:

<?php if( is_page(‘129’) || is_child(‘129’) ) {
wp_nav_menu( array( ‘menu’ => ’10’, ‘depth’ => 1 ) );
} //vintagemenyn
elseif(is_page(‘141’) || is_child(‘141’)) {
wp_nav_menu( array( ‘menu’ => ’11’, ‘depth’ => 1 ) );
} //retromassan
else {
wp_nav_menu( array(‘menu’ => ‘Hem’, ‘depth’ => 1 ) );
} //alla andra
?>

The function:

function is_child ($parent) {
global $wp_query;
if ($wp_query->post->post_parent == $parent) {
$return = true;
}
else {
$return = false;
}
return $return;
}

My problem is that I also need to put the menu on the grandchildren of the pages, wich isn’t working right now. Can somebody help me? Thanks!