Yeah, I'd definitely say Pearl Harbor got fired upon in WWII. Not to mention Attu and Kiska (in the Aleutian Islands) - they were not only fired on, they were occupied and held by the Japanese for an extended period.
He probably meant "on the US Mainland".
Back on topic, Astoria is nice, but getting there will require at least a little backtracking (Astoria is north of Portland). I'd consider staying someplace a bit further south on the coast - Cannon Beach would be perfect, or someplace south of there. Your problem is that the Oregon Coast has way too many worthwhile things to see and do. You only have, what, 2 days on the coast? - you will be constantly tantalized and frustrated because you will want to stop and spend time at places you see every 5 minutes as you drive the length of the state. 101 (the route along the coast) is mostly 2 lanes and very curvy, with stunning views every couple of minutes (and no shortage of traffic, a mix of everything from gawking tourists like yourself, to fully loaded logging trucks - be careful), so the drive will be slow, and it will take you longer than you think to get to destinations. That's OK, just looking out the window will put a smile on your face. There's no place in the world more beautiful than the Oregon Coast.
If you're overnighting in Newport, be sure to go to Mo's for clam chowder - it's an institution (and the chowder is good, too).
I'd skip the observatory at Mt. Saint Helens - it's gonna be a long detour away from your route and the time driving up there and back will significantly eat into your destination time on the Oregon Coast. I've jumped in my car in Seattle and made a beeline for the Oregon Coast many times. If I were you, I'd do it this way: jump on I-5 EARLY (Seattle area traffic is miserable, try and get out ahead of it - like before 7 am if you can). Head straight down I-5 to Portland (watch out for the State Patrol especially in the areas from around Tacoma to south of Olympia - lots of speed traps around there). Skip the Johnson Ridge Observatory side-trip. In Portland, take Highway 26 and stay on it until you reach the coast, just north of Cannon Beach. That's a good place to start your Oregon Coast trip, be sure to get out and stretch your legs here (you'll need it). From there, slow down.
Your trip sounds like you only get 2 days at the coast, and you're only going as far south as Newport. The great stuff continues south of there - try and see a little more if you can. Honestly, with the number of days you have, I'd gladly lose a day in Portland and/or Seattle, and use that day to see/do/enjoy more of the Oregon Coast. I live in Seattle and used to live in Portland, know them well. Honestly, they're a lot like any other city and despite all the hype, they ain't all that special (used to be, not so much after the past decade's booms). The Oregon Coast hasn't been ruined yet and is still very special - see it while you can. Personally, I'd trade any day in Seattle or Portland for a day in Yachats or Florence.