The ruins to the south? Yes, light cover. Rocks and cliffs as well.
Patches of trees, I'm not sure. Logic says that any tree hit by your weapons - or the monster's - is going to become sawdust pretty much in one hit, and trying to track which trees have been destroyed and which not might be kind of a pain.
Looking at the map, let the mechanized infantry pound away at the swarms. While that's happening, I'm thinking Kingsley will swoop downwards and engage the enemies, keep them away from Abigail. Harvey can handle anything that gets past the pit traps and Abigail can help whoever needs it. That sound good?