L.F.
Your son might be a little too young to appreciate it, but when I was a kid, I just loved our trip to the Tillamook Cheese Factory. They have great ice cream there!
There is also the Oregon Coast Aquarium in Newport. And there is a little beach called Neskowin that (as of nine years ago) is fairly secluded. Might be a good place for a beach picnic. Good luck to you! I miss my home state of Oregon :-)