I peeked in the nest this evening and found the eggs hatched, except for one so far. The hen, which I'll figure out what the name of the bird is next, sat on the edge of her nest until I was about two feet away. Then she skittered off into the protection of a hollyhock's ground level leaves and scolded me as I showed the kids her nest. The picture doesn't show much more than a few fleshy lumps and some fuzzy feathers. But moments before I took the pic the nest was nothing but yawning beaks. We finally gave her privacy and moved back deeper into the garden to plant carrot seeds and bust up the ground some more for another round of beets. I then heard her scolding again and took a few steps toward her nest and saw two larger birds (might've been red wing blackbirds) leave the blooming crabapple tree that's right in front of there. I hope she stays hidden from any other predators, poor babies.
Editing to update: It's some sort of sparrow... maybe Grasshopper Sparrow's nest.