In all honesty this is a silly exercise.
Those trees should just come down. They are old pine of some sort and look close to the end with the way they have lost most of their lower limbs.
I would push to remove trees, grade/roll the lawn down to meet the curb, maybe using the material excavated to create a raised bed or smaller burm somewhat more inside the curb area.
I would think about planting some landmark trees like a nice large multistem red maple, tulip poplar which grow quickly and are quite interesting. If they are set on evergreen go with a a few nice Norway Spruce in a sweep/informal planting.
When planting I really like to stick with "old favorites" A hedge of sorts there to create some privacy and intimacy in the yard would be nice. Plants like common lilac, Juneberry, red buds, dogwood, magnolia, roses, etc etc. Really don't like that suburban weepy crap look.
We try to avoid walls whenever possible. There is a place for SRW walls but in my mind most of them are just something that you are going to be paying to tear out and dispose of again in the future when they fail.
I like to do something that is appropriate and makes sense. Most owners seem to understand that when you really explain that to them. Oddly I find myself agreeing with DVS here...
My 2 cent ramble...