I guess if this is going to be the default register form, you can add a 301 redirection to the new form URL.
Community events uses the default WordPress function wp_register to show the register link, you can filter the ouput to change the URL. Add this snippet in your functions.php file to do so:
/**
* Modify register URL
*/
function custom_register_url ( $url ) {
return site_url('register');
}
add_filter( 'register_url', 'custom_register_url' );
Be sure to change the URL for the one you created.
Best,
Nico