I'm flying PTY-LAX in April with my family in coach on a UA award. I am Star Gold (UA 1k). Can I get seats assigned now? The website doesn't provide the option when I pull up the reservations and 2 agents said its at check-in time only. Ideally I'd like to snag Row 5 for us (kids are too young for exit row). Its my first time on CM and that too in Y.