Custom Entity Administration Pages
A little bit late, however, hope this will be of use.

When defining an admin path for each bundle, path provides the path that should be used in hook_menu for the Field UI´s pages. For resolving the '%event_type' placeholder in admin paths, you need to provide a loader function that, in your case, should be 'event_type_load' and it must return a single type object.

/**
 * Event type loader function.
 *
 * param $type string
 *  The name of the event type as it appears in the admin Path placeholder 
 *  of a bundle. By convention, all Drupal paths use dashes instead of underscores.
 * 
 * return $type stdClass object
 * 
 */
function event_type_load($type) {
        $types = enf_get_types();
        // We need to replace dashes that may appear in $type with underscores.
        // By convention, bundle names needs to use underscores, not dashes.
        $type = str_replace('-', '_', $type);
        return isset($types[$type]) ? $types[$type] : FALSE;
}


You may need to modify as well the line that reads,

'real path' =&gt; 'admin/structure/enf-event-types/manage/' . $type,


and replace it with the following one:

'real path' =&gt; 'admin/structure/enf-event-types/manage/' . str_replace('_', '-', $type),


NOTE: to be consistent with the name of the module that defines your custom entity, you may want to rename the admin path placeholder '%event_type' to be '%enf_event_type', and thus the loader function would be 'enf_event_type_load'.