It would probably be a good idea for the Mets to move the promotion to a different afternoon. Very young kids aren’t going to be able to stay awake that late regardless of the calendar. (Though I doubt parents were going to be able to get two- and three-year-olds through the Banner Day festivities and a full nine inning game no matter when it started.)
I think it would be fun if the team worked something out to move the Binghamton Mets vs. Portland Sea Dogs game from NYSEG Stadium to Citi Field to turn the day into a twi-night doubleheader with Banner Day held between the games. (If the pitching rotations worked out, how great would it be if Noah Syndergaard got to make his first big impression on the New York media and fans at Citi Field on Banner Day?)
But the Mets aren’t showing any indication that they’re going to reschedule Banner Day and moving minor league games costs money, so I don’t really expect the team to do either.