change custom text field to textarea in general settings

Greetings, I am trying to add a text area to my general settings in worpress multisite (so that store owners can have their store policies displayed)
I have managed to add a text field and display it on a dedicated page. However the text field is too small and I would like to have at least a text area (a visual editor would be ideal but i'm not picky) also a description would be nice if possible.
Here is the code I have now. It is pasted in my functions.php file

class new_general_setting {
function new_general_setting( ) {
add_filter( 'admin_init' , array( &$this , 'register_fields' ) );
}
function register_fields() {
register_setting( 'general', 'store_policies', 'esc_attr' );
add_settings_field('store_policies', '<label for="store_policies">'.__('Store Policies:' , 'store_policies' ).'</label>' , array(&$this, 'fields_html') , 'general' );
}
function fields_html() {
$value = get_option( 'store_policies', '' );
echo '<input type="text" id="store_policies" name="store_policies" value="' . $value . '" />';
}
}

Is there a way to do this, I'm sure it must be pretty easy for those who know what they are doing (unlike myself). Any help would be appreciated
Cheers
Meriam