JJ NextGen Carousel conflicting with other plugin

I am trying to run two JQuery-based plugins on the same page — the Nivo Slider and the JJ NextGen Carousel.

When I try to run them both, the Nivo Slider breaks — though it is still semi-functional, its transitions from slide to slide no longer work and its prev/next arrows don’t work.

I believe this is because I am calling JQuery twice. I’m not sure how to avoid this situation, though. Do you have any advice?

I am calling the JQuery for the Nivo Slider in the header.php file, using this code:

<?php wp_enqueue_script('jquery'); ?>
<?php wp_head(); ?>

Followed by this set-up of the JQuery:

<script type="text/javascript">
jQuery(window).load(function() {
	jQuery('#slider').nivoSlider();
});

For the NextGen Carousel, the plugin calls the JQuery using this code in its own function.php file:

function WPJJNGGJ_CAROUSEL_enqueue_scripts()
{
  if( !is_admin() )
  {
    wp_enqueue_script ( 'jquery');
    wp_enqueue_script( 'jquery-jcarousel', WPJJNGGJ_CAROUSEL_plugin_url( 'script/jquery.jcarousel.min.js' ), array('jquery'), '', false );
    wp_enqueue_script( 'jquery-shuffle', WPJJNGGJ_CAROUSEL_plugin_url( 'script/jquery.jj_ngg_shuffle.js' ), array('jquery'), '', false );
  }
}

Any thoughts would be greatly appreciated.