Need to get specific data from array

I’m building a custom carousel for a client. I’ve got a function which gets blocks of three images from all of the images attached to a post:

global $rental;

$images = get_children( array(
    'post_parent' => $rental_id,
    'post_status' => 'inherit',
    'post_type' => 'attachment',
    'post_mime_type' => 'image',
    'order' => 'ASC',
    'orderby' => 'menu_order ID'
) );

$array = $images;
$number_of_elements = 3;
$count = count( $array );
$split = array();

for ( $i = 0; $i <= $count - 1; $i++ ) {
    $slices = array_slice( $array, $i , $number_of_elements);
    if ( count( $slices ) != $number_of_elements )
        break;

    $split[] = $slices;
}

if ($split) :
    foreach ($split as $outeritem) :    
        echo '<div class="Outer Top">';
            foreach ($split as $inneritem) :
                echo '<div class="Inner Top">';
                echo '<img src="' . $inneritem . '">';
                echo '</div>';
             endforeach;
        echo '</div>';
    endforeach;
endif;

//print_r( $split );

All I need to finalize this is to replace inneritem with the URL of the image. The data is all there in an array, and as you can see I just need to pull the value of guid for each item. The array below comes from uncommenting the print_r( $split ); and I’ve removed all the extraneous data for the sake of tidiness:

Array (
    [0] => Array (
        [0] => WP_Post Object (
            [ID] => 120
            [guid] => http://******/wp-content/uploads/2016/12/T15923-11-1-1.jpg
        )
        [1] => WP_Post Object (
            [ID] => 121
            [guid] => http://******/wp-content/uploads/2016/12/T15923-12-1-1.jpg
        )
        [2] => WP_Post Object (
            [ID] => 122
            [guid] => http://******/wp-content/uploads/2016/12/T15898.jpg
        )
    )
    [1] => Array (
        [0] => WP_Post Object (
            [ID] => 121
            [guid] => http://******/wp-content/uploads/2016/12/T15923-12-1-1.jpg
        )
        [1] => WP_Post Object (
            [ID] => 122
            [guid] => http://******/wp-content/uploads/2016/12/T15898.jpg
        )
        [2] => WP_Post Object (
            [ID] => 123
            [guid] => http://******/wp-content/uploads/2016/12/T15923-13-1-1.jpg
        )
    )
    [2] => Array (
        [0] => WP_Post Object (
            [ID] => 122
            [guid] => http://******/wp-content/uploads/2016/12/T15898.jpg
        )
        [1] => WP_Post Object (
            [ID] => 123
            [guid] => http://******/wp-content/uploads/2016/12/T15923-13-1-1.jpg
        )
        [2] => WP_Post Object (
            [ID] => 124
            [guid] => http://******/wp-content/uploads/2016/12/T15923-14-1.jpg
        )
    )
)

You should be able to rewrite what you have about and also use get_permalink as @Benoti stated while omitting the $split array.

get_permalink accepts either the Post ID or a post object.

global $rental;

$images = get_children( array(
    'post_parent' => $rental_id,
    'post_status' => 'inherit',
    'post_type' => 'attachment',
    'post_mime_type' => 'image',
    'order' => 'ASC',
    'orderby' => 'menu_order ID'
) );

$array = $images;
$number_of_elements = 3;
$count = count( $array );

for ( $i = 0; $i <= $count - 1; $i++ ) {
    $slices = array_slice( $array, $i , $number_of_elements);
    if ( count( $slices ) != $number_of_elements )
        break;

    echo "<div class="Outer Top">";
    foreach( $slices as $inneritem ) {
        $link = wp_get_attachment_url( $inneritem->ID );
        echo "<div class="Inner Top">";
        echo "<img src="https://wordpress.stackexchange.com/questions/251866/$link">";
        echo "</div>";
    }
    echo "</div>";
}