Just returned from the north coast, here are my thoughts...
If you are a first time visitor to the Oregon Coast, then Newport is an excellent place to visit. The Oregon aquarium is wonderful and a trip here will help you learn about tidepools and the coast in general. The tidepools at Yaquina Head (just north of Newport) should be your next stop and they never fail to amaze. Everywhere you look, there is something. As always, be safe when on the coast and be sure to be smart about the tides. The "beach" is pretty cool as it is a black rock beach and the lighthouse is there also. The Rogue Brewery (south of the bridge in the same general location as the aquarium) is nice if you like that kind of place and I think the food is usually better there than the restaurant downtown. There is also the University aquarium. Good access to sandy beaches, nice marina, lots of places to eat, shop, do the tourist thing. My mom always likes the sea lions hauled out on the docks by the fish processing place. Plus some interesting little neighborhoods like Sylvia Beach and Nye Beach. Most likely is probably is a 3 hour drive from Portland so be sure to take that into consideration.
If you know something about the coast, are tide savvy, tidepool savvy, and are looking for places to hike, the north coast is nice. I went to Oswald West State Park and the beach is smallish, protected by two capes. Also known as "Smuggler's cove." Tons of surfers. The tidepools were nice but somewhat limited. Not what I would recommend for a novice or first time experience. Things may be different at Canon Beach, but I did not make it there this trip.
I meant to pull out some old photos from Yaquina yesterday, but I forgot and now I'll be out of town until the end of the week for work. Bummer. Let me know if you're interested and I'll post them when I return.