Looks like the apron is still in progress, but yes make sure to cover corners as well and not sure how you're attaching them to the coop itself, but consider screwing it into the coop trim for a good secure fit (note the screws and washers at bottom of my coop... since my coop is fully internal in the run I only put 1 screw per foot or so).
Adding ventilation via some louvered vents might work well for you, as they shouldn't be too hard to add (cut an opening, place vent cover, add hardware cloth on back side) and will help ward rain off the openings even without much roof overhang.

Adding ventilation via some louvered vents might work well for you, as they shouldn't be too hard to add (cut an opening, place vent cover, add hardware cloth on back side) and will help ward rain off the openings even without much roof overhang.