partly germinated seed flats: cover or not?

[habitat_gardener]

I'm planning to go away for a couple days, right in the middle of the Great Germination.

Usually I plant in separate containers, but this year I used some connected cells. So I have flats where a few seeds have germinated and are reaching for light, but most seeds have not germinated. If I were home to babysit them all day, I'd move them outside for a few hours and monitor the moisture levels.

I germinate indoors, next to a window, and plan to move the seedlings to the greenhouse when they have all emerged.

For the days that I'm not here (and don't have someone reliable to take care of the seedlilngs), should I lightly cover the flats (piece of plastic a couple inches above the pots) so that the newly emerged seedlings don't dry out? Or leave it all exposed to the air?