The drive up the (I think) 101 along the coast of Oregon is very nice. Lots to see that way and some great twisty roads, although it will take a little longer than using the I5. There's a great aero museum at
Tillamook. Somewhere along there you can visit the Spruce Goose, too. I didn't get a chance when I was along there last, though. Personally I hate those interstate highways, they bore me to sleep. But if your time is limited, I guess that's what you have to do.
The drive along the (I think) 97 on the east side of the mountains is also very scenic (in parts)(since you mentioned going through Bend). Flat plains with the occasional cinder cone and deep river gorges at the north end of the plain are quite spectacular. You might be able to visit Crater Lake which is a bit of a detour from the 97 but is probably closed this time of year anyway. Snowy up there, you know.
In Seattle, there's a great chili place in the Pike Place Market with a name like "Worlds Greatest Chili" or somesuch. You probably get good chili in California already but we don't get much up here so I often visit when I'm down there.
Anyway, there're a couple of ideas.
EDIT: I second Island's recommendation of seeing Mt. St. Helens. Very impressive and humbling. (I'm not sure if the road from the north is still open, not the new one from the interstate. It wound up through the forest until you came out into the clearing made by the blast where all the trees are laying down flat radially away from the crater, and there was an old charred car left on the side of the road from that day. I remember it being much more impressive than the relatively sterile new route, although a lot of the same things can be seen. Probably not in your timeframe, though.)