Yes, a fun trip. Sometimes they run the Heisler (geared), a nice change from the ALCO in your photo.
There is good ice cream at the far end of the trip.
Will you have a car? If so, ride the trolley along the waterfront in Astoria (and check out the architecture on the hill above town), sample cheese and maybe have lunch with the goats at Blue Heron in Tillamook (a little north of the Tillamook everyone knows about), the big Tillamook Cheese factory has a pretty good tour (and Huckleberry ice cream), and spend a day at the Tillamook Air Museum where they restored that ALCO McCloud #25 and you can watch and talk to the people restoring planes. It is also an incredible space, one of the WWII airship hangars.
In addition, if you have a car and school age kids, you will be very close to some Lewis and Clark camps.
Blue Heron: http://www.blueheronoregon.com/
Tillamook Cheese Factory: https://www.tillamook.com/
Tillamook Air Museum: http://www.tillamookair.com/