Thanks for all the responses. My only concern is all the emphasis on "properly". Is aerating and the various spray/fertilizer mentioned here pretty easy to do if you follow the instructions?
Here are some wider photos a few were asking for. I do have a few areas where there isn't much grass and an area in the front (between the trees) where water sits when it rains a lot. These photos are outdated as I've cleared out the beds in the front and trimmed back the trees a bit, but you get the point.
Backyard - I don't have any grass (nor do I care to) back between the trees in the woods