Newbie question from a United convert. Flying on a short international flight in a week or so (MIA - PLS) and looking to bump up to Group 5 (family of 3 w/o status). That said, there's only exit row MCE seats left. Can I purchase MCE for myself and then "give up" the seat (move back to a regular seat to be near family) while retaining the benefits - most importatnly the earlier boarding group? I don't need the checked bag, just want to ensure we get overhead space and not sure of any other way to buy priority boarding?