or you can simply disable fancybox in your theme directly:
and dont't care of the option in option page ;)
by using something like that:
if( wp_is_mobile() ) {
wp_enqueue_script('ngg-photoswipe-disable-fancybox.js',get_template_directory_uri().'/js/ngg-photoswipe-disable-fancybox.js', array( 'jquery' );
}n.b.
copy ngg-photoswipe-disable-fancybox.js from plugin directory in your theme directory