I am from your area and have a couple plantings along tree lines similar to you.
I use daffodils they make a nice row and multiply with out any help, look good in the spring are dense enough to keep other things away
Then in front of the daffs I plant hosta in the shady areas and daylilies in the sun these come up and cover the dying greens of the daffodils.
Ideally you might add a couple under-story shrubs / trees
My favorite are red-bud or dogwood trees and service berry bushes (amelanchier)
Then you can think what you want among the trees , in the wooded area
Like bluebells, woodland phlox...etc
