Ransom said:
Lots of good stuff above; before refreshing the page I was about to add WAAAM. It's impressive (and Hood River is a neat little town, so there are some neat sightseeing things in the area; I'm not sure how to recommend them since everything I see in that area I do by mountain bike).
OMSI's great, but if you do fly into S.F., I'd recommend the Exploratorium, which is one of the places I really had my childhood imprint of scientific wonder. But not getting out of S.F. immediately probably complicates things, as well as adding a bunch of other opportunities...
My BIL/SIL own Waucoma bookshop on Main street in Hood River, which is more or less a great place to stop and get some recommendations for places to eat and places to see while you're in town.
That said, the WAAAM museum is really wonderful and worth the trip, especially if you hit Multnomah Falls on the way there or on the way back.
There are other places to stop along I84 (Vista House for example), unfortunately much of Old Columbia River Highway is still closed along with a few places along the way due to the fires from last year.
McMennamins Edgefield (former Poor Farm) is in Troutdale along I84, and has several places to eat and grounds to explore, etc.
Boeing's Museum is pretty impressive and worth a stop if you're in the area.
The McMinnville Evergreen Museums (Where the Hughes H1 aka Spruce Goose is located) they have a space museum that does a great job showing the progress of both the US and USSR space efforts. There's a water park too if some energy needs to be burned off.
OMSI is great, especially the WWII sub tour, but if I were in SF or Seattle I'd hit their Science Museums over OMSI if I had to choose. MoPOP in Seattle is great too.
Astrophotography is awesome and very popular in Southern Oregon in the Bend/Redmond area along with Crater Lake, etc. There should be some groups in the area that might help with any interest in it.