Set page to draft on plugin deactivation

I’m posting this as another solution for you and its based on the page id

/*
$post_id - The ID of the post you'd like to change.
$status -  The post status publish|pending|draft|private|static|object|attachment|inherit|future|trash.
*/
function change_post_status($post_id,$status){
    $current_post = get_post( $post_id, 'ARRAY_A' );
    $current_post['post_status'] = $status;
    return wp_update_post($current_post);
}

So once you have this function you can use it with the page id of the page you created:

$ads_page = get_option('mjj_smart_ads_page');
$old_ads_page = change_post_status($ads_page,'draft');
update_option('mjj_old_smart_ads_page', $old_ads_page);