private function getRandomActivityIds()
 {
     $activityIds = App\Activity::lists('id')->toArray();
     $randIds = array_rand($activityIds, 3);
     unset($randIds[0]);
     //some more extra randomness...
     if (rand(0, 1) == 1) {
         unset($randIds[1]);
     }
     return $randIds;
 }