I would say bring Mickey 100%! Horse shows aren't the best place to bring a dogs that needs socialization, she could try and socialize with a horse and get kicked! Both my dogs spend a lot of time around horses and at barns and Lady is much calmer than Toby, therefore better around horses than Toby. You don't want Molly to get board and start barking and other things, since she will have to be on a leash at all time, that can spook the horses.