Emerald Arborvitae is supposed to grow to 15' at the most, so it won't serve the purpose you want. Its cousin, "Green Giant' might be the answer. It's supposed to grow to 30'. I have 'Emerald'. It grows quite dense and fast enough for me. I need to tie the multiple trunks in winter, though, because they will bend down every which way under snow. If you can find a single trunk tree, you'll eliminate that trouble. Dawn Redwood is deciduous. You'll lose the noise and view barrier in winter. I don't have experience with other trees. My garden is too small for them. A small blue spruce came with the house, but I had to remove it after 15 years because it grew too large for the spot. Good luck with your choice. I think a few different kinds of conifers might be more beautiful and interesting than just one kind. They give you different colors, shapes and textures.

Crinum X powellii is sold at local outlets, seen growing against warm walls. (The 1990 winter may have reduced the number of some of the old clumps, I have never taken a survey). I first saw large, impressive ones at Butchart Gardens. My current favorite local specimen is a somewhat deeper pink one ('Ellen Bosanquet'?) NW of an old house on a busy street in central Seattle. Its large, straplike, flopping leaves and trumpet-flowers hang out over the sidewalk, weeds, trash, dirt and scaffolding (the place has been under renovation every time I've driven by, for years) all around it. When in bloom it looks like a busker playing a cheerful tune in the midst of urban drab.

Melodiek~ My parents live in not too far south of Bellingham in town called Mt Vernon. Don't miss the tulip festival there, it's breathtaking! Their weather is a bit more tempered than in B'ham, where there can be some nasty ice storms. Having had the pleasure of watching a soccer game up there one year when the sideways rain turned to ice.... well, let's just say you aren't thinking what to plant right about then! There are some wonderful apple orchards in the town of Lynden, not far from Bellingham. Wet and cloudy, yes it will be. But it really makes you appreciate the drop-dead gorgeous views over the sound when the sun comes out!!!

Agree that a small outdoor area given over to large dogs in particular = equivalent to zoo exhibit. In other words the impacts from the dogs will dominate how it looks (and smells), how it will have to be managed. Regarding the neighbor the natural choice for a screening planting in your climate and soil conditions is western redcedar (Thuja plicata). With there being an existing landmark sized example visible in the distance, just to the right of your house. And maybe a grouping of currently smaller ones over the fence, behind the two broadleaf trees. Such an installation can be sheared to control size once the desired level of privacy is acheived. As long as the lower sides are kept wider than the upper half, so as to prevent the upper shading the lower too much and making it become thin looking. This is how it usually is with plant choices for hedging and screening - the fast growing ones that provide the desired effect with any level of quickness are also large growing, genetically programmed to grow vastly bigger in time than the typical modern planting site. And the comparatively small growing and naturally tidy kinds often need decades to reach even human head height level.