Contextual maps with multiple pages being called

I have the following pages:

– UK
— Cambridge
— Oxford

Cambridge and Oxford render their markers just fine using <?php echo GeoMashup::map(); ?> (I need to load the map elsewhere in the page), but is there a way to load both of them in the parent page?

I am rendering all the child of UK using page-list‘s tag [pagelist_ext], however this seem to lose the contextual reference for geo-mashup.

Is there a way to make it work?

Alternatively, I wrote this which does the trick from header.php but I don’t know whether it is the best way to do this (I’m new to WP)

<?php
    $custom_query = new WP_Query( array(
        'post_type' => 'page',
        'post_parent' => $wp_query->post->ID,
    ) );

    if ( $custom_query->have_posts() ) {

        echo GeoMashup::map( array(
            'map_content' => $custom_query,
        ) );
    }
    ?>
    <?php echo GeoMashup::map(); ?>

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