Accessing value from associative array

You’re doing one to many loops. What you want to be doing is this:

$args = array(
    'child_of' => $CurrentPage
);
$children = get_pages( $args );
foreach ($children as $key => $value) {
    echo $key['post_title'];
};

Or you could also:

$args = array(
    'child_of' => $CurrentPage
);
$children = get_pages( $args );
foreach ($children as $child) {
    echo $child->post_title;
};

It’s entirely up to you, but since you already know what elements each $child has, why not stick to the same syntax as used in the get_pages() Codex article?