I interpreted dressing-up to be putting on a "brave face" or pretending.
As I started composing the image I imagined the characters to be an unhappily married couple dressing-up for some sort of strained social occasion (like a relative's wedding). The woman dresses up in a fancy hat and the man "wears" a smile. They pose as a happy couple though secretly they can't stand each other anymore.
But now as I look at their expressions, their faces seem to suggest grief more than anything else. Perhaps it's not that they have an unhappy marriage but it's that they have recently experienced a loss and are putting on a brave face in public.
Either way, rather bleak. Maybe Lizzie's will be more cheerful!