You could use a bit of jQuery in the footer, my JavaScript is not that good but something like this could work if you add it to your footer just before the closing body tag:
<script>
if (jQuery(window).width() < 800) {
jQuery(".menu-item-has-children a").removeAttr("href");
});
</script>
As a rule though avoid adding links to parent menu items as this confuses users. I normally just add a # tag with the menu item name and then remove it after it is part of the menu.
Thank you. The custom menu item solution is the easiest and best. Works great now.