You are on the very northernmost boundary of the area in which oleaders are winter hardy. As long as our mild winters continue, you'll be okay. But one hard winter, and you lose the bet. Your chances are slim to none with Sago palm (cycas).

Food for thought: typically, a home looks most grounded when it is landscaped with a strong sense of place. In other words, beach style landscaping looks natural and right on the coast, but may well look very artificial and out of place at the foot of the Great Smokies.

Also, oleander requires alot of space. It gets really big, and you can prune all you want, but it will keep on getting really big. It is also a pretty rangy looking plant. It never really fills in solidly. And, the blooms, though lovely in arrangements and bouquets, tend to sag and flop on the plants. And yes, all parts of the plant are poisonous.

I suggest you get a copy of The Southern Living Garden Book. It has many useful plant lists, an exhuastive list of plants that grow in the south, and guidelines as to which of those plants will grow in which parts of the south. The phrase, "knowledge is power" was coined, I think, for gardening in the southeast.

Some oleanders are hardier than others but I don't know which are which. A neighbor across the street brought one back from their place in Destin and planted it here, in Hueytown, AL. It didn't make it through the first winter. Another neighbor down the street has a dark red oleander and it has been healthy for several years. Have you considered planting native scrub palmettos? They are hardy in this area. I grow oleander as a pot plant and it blooms and blooms. The palmetto would take care of your evergreen needs and the potted oleander would give you blooms in warm weather. Often the oleander blooms throughout the winter in the greenhouse.

I'd reconsider your options. There is a slim (SLIM) chance that oleander would survive in your location. Even if the roots weren't killed outright, your plants would be top killed on an annual basis, and never become the tall shrubs that your wife desires.

Also, these shrubs need the full sun in order to thrive. So there are two marks against you. Add to that the fact that they are very toxic and I think you'll come up with the right decision.