I had a similar situation at my house (Richmond, VA) when we bought it a few years ago. The previous owners had planted plenty of trees and shrubs in the beds and throughout the yard, but for some reason, did not plant anything within 5' of the foundation along the entire front of the house. It looked naked, so I knew I had to plant something there but our mostly shade location limited our shrub choices. After driving around my 'hood and other neighborhoods nearby looking for successful foundation plantings, I decided my best options were cleyeras, nandinas and japanese hollies. I really wanted boxwoods, but I saw too many older plants with obvious loss from storm damage-- they looked kind of like a toothless smile. I've since planted cleyeras and nandinas out front, and the japanese hollies in some of the back beds. So far, everyone is doing well. Nandinas, hollies and cleyeras may not be terribly unique or exotic, but their widespread use makes them easy to obtain and affordable even in a large pot size.

Can you give us more info on the "full sun to full shade" issue? Full sun would be 6 or more hours of direct sunlight, Partial sun/shade is 3-6 hours of direct sunlight, and full shade is 3 or less hours of direct sunlight per day. Here is a link that might be useful: What Does Full Sun Mean?

Hydrangea arborescens 'Annabelle' won't exceed 4' height, but it does sucker and if not managed will increase in width. There are several reblooming (remontant) Hydrangea macrophylla that even if they are hit by spring frosts will bloom well over the summer. All are happiest with afternoon shade. Rhododendron 'Checkmate' (a short version of the PJMs), R. 'Yaku Prince', as well as some others if you have acid soil. I also have a Leucathoe which has never exceeded 4' without pruning, and L. 'Rainbow' while listed as 3'-5' is slow enough growing so that it can probably easily be kept below 4'. It has quite ornamental leaves, but also likes acid soil. Both the Rhododendrons and the Leucathoe are evergreen. Several of the small Deutzias, such as 'Chardonnay Pearls', 'Nikko', 'Yuki Snowflake' will bloom well with half shade (mine get afternoon shade.) In my garden they top out at about 3 1/2 feet. One of my favorites, a semi-evergreen plant with white-edged leaves and a long, though never stunning, bloom time, is Daphne x transatlantic 'Summer Ice'. It is often both the first and last blooming shrub in my garden. Scented, and I have found it to not fit the reputation of fussiness that many Daphnes have.

IF one of the trees is a silver maple, you might want to think about taking it out. Silver maples are notorious for dropping limbs as they get big. I don't know the law in Canada, and think it varies from state to state here, but I THINK the owner can be held liable for limbs that land on other people's property - since the trees in question are next to a street, it's something to think about. I don't know which tree IS the silver maple, nor what shape the scaffold/structure of branches is in, but it would give more light to the area. Some (depending on species) of the other maples aren't quite as aggressive with surface roots. You could limb up some of the trees, and get more light in that way too. I can certainly see why you want shrubs there, it's just a matter of finding them. Vines along the fence, as long as they aren't TOO aggressive, would be one way to give privacy. Evergreen vines are more difficult. Even though it can be an invasive thug, and would eventually need careful pruning, esp. to keep it out of the trees, ivy, I think, can take your winters if you aren't too cold - maybe not. (It's been too long since I lived/gardened in the North to remember!) Since we don't know your zone, it's a little harder to make suggestions. Clematis would grow, but might not flower, and they are deciduous. Grape vines the same, as with Boston ivy. Hardy kiwi vine, five-leaf akebia and AMERICAN (NOT the Japanese, it's an invasive thug) bittersweet, might also do, with the same caveats - few or no flowers and they are deciduous. You could try an non-invasive berberis, if such exists. Aronias or amelanchiers might grow - probably no fruit/flowers, and they would need pruning since they will try to grow to light. Ceanothus americana - New Jersey tea - might do - and might be hard to find. With watering, Clethra alnifolia might grow, and might flower. Some of the shrubby dogwoods might be OK. Fothergilla is another possibility, but might be too small. One of the deciduous hollies is another thought. And one of the native azaleas might survive. I would research all these to see what will do well for your area, and which are available in your area, which may not both be the same thing!