Shortcode array in array (custom taxonomy)

I am using a widget, U more recent posts. Seems to work with custom taxonomies when you input the correct data into it in a widget form, but the suggested shortcode doesn’t work (and I am trying to insert it into a post).

He suggests including the following query in the shortcode;

tax_query="taxonomy=category&terms=14,17"

so I have tried….

[u_more_recent_posts id="hue-recent-posts" tax_query="taxonomy=destinations&terms=174" post_type="post"]

where destinations is the name of my custom taxonomy and 174 is the id of the posts I want to display.

I am sure, I just need to alter the shortcode slightly for it to work, but have been trying for hours and can’t work it out!! Any help would be ENORMOUSLY appreciated!!

I think the relevant code in the plugin are;

if( !empty($opts['post_type']) ) {
		$query_args['post_type'] = $opts['post_type'];

		if( !empty($opts['tax_query']) AND isset($opts['tax_query'][$opts['post_type']]) ) {
			$tax_query = $opts['tax_query'][$opts['post_type']];

			if( !empty($tax_query['taxonomy']) AND !empty($tax_query['terms']) ){
				$tax_query['terms'] = explode(',', preg_replace('/\s*/', '', $tax_query['terms']));
				$_tax_query = array(
					'taxonomy' => $tax_query['taxonomy'],
					'terms' => $tax_query['terms'],
					'field' => 'id',
				);
				$operator = '';
				switch($tax_query['operate']){
					case 'include': $operator = 'IN'; break;
					case 'exclude': $operator = 'NOT IN'; break;
					case 'and': $operator = 'AND'; break;
				}
				if( !empty($operator) )
					$_tax_query['operator'] = $operator;

				$query_args['tax_query'] = array($_tax_query);
			}
		}
	}

and this bit…..

if( isset($atts['tax_query']) ){
		$opts['tax_query'] = array($opts['post_type'] => wp_parse_args(preg_replace('/&/', '&', $atts['tax_query'])));
	}

Thanks very much in advance for any help, I am completely stuck!!