<ul>
<li><a href="<?php echo get_option('home'); ?>/"><span>Home</span></a></li>
<?php
$pages = wp_list_pages(’sort_column=menu_order&title_li=&echo=0′);
$pages = preg_replace(’%<a ([^>]+)>%U’,'<a $1><span>’, $pages);
$pages = str_replace(’</a>’,'</span></a>’, $pages);
echo $pages;
?>
</ul>