Custom author search

Jus add the parameter 'author__in'=> array( 2, 3, 5 ) to $args and pass the author ID or IDs. You’ll get the results.

$args = array(
    'author__in'=> array( 2, 3, 5 ), // array of authors IDs you like to include
    'post_type' => 'post',
    'post_status' => 'publish',
    'posts_per_page' => -1,
    'caller_get_posts'=> 1
);

And I don’t think you need the $my_query = null; to nullify the variable before declaring it.