I found this to work.
foreach ($uncatChildren as $k => $child) {
$options[] = array('value' => JRoute::_ ('index.php?option=com_virtuemart&view=productdetails&virtuemart_category_id=' . $virtuemart_category_id . '&virtuemart_product_id=' . $child['virtuemart_product_id']), 'text' => $child['product_name']);
}
array_unshift($options,"Please chooose an option"); // this pushes the option to the top of the list.
However, I am still looking for a way to now require that something get picked.