Thanks for all the suggestions -- good food for thought. I bought my son a nice sized oak-leaf hydrangea which is a very handsome somewhat manly plant. I had read that the oak-leaf variety are more deer resistant ... ?? The tag designated it as 'full sun' which is surprising to me, but when I asked the nursery gal about that, she looked it up online and found that is can more easily tolerate full sun than other hydrangeas.
Second son measured off the yard and will come up with a couple plans (high end spendy to more economical less splashy) and I'll dig up some of my own plants to help fill in the planting areas. I also have access to native ferns and berries and vine maple (hard to transplant), so we may be able to set him up with a native feel.
First son's thought is if he has a plan to follow, he can kind of pick at it as his funds allow - put in the hardscape a project at a time and fill in with plants as he can.
Second son has I think convinced first son to take down 3 rather scrappy diseased but mature trees in his back yard - a suckering ash, spindly fir, and half-dead pear. That will open up a huge amount of sun to his east yard, and give him a pretty blank slate to start fresh.
I'll try to take photos as this project unfolds, might be interesting to follow.