Come see the riverwalk, and maybe start at the East End (at the old 39th st. cannery) and have coffee at Coffee Girl.
Along the riverwalk, there's much to see and do, and even places to eat.
The Rio Cafe is great Mexican food (located on 9th st. near the Sunset Empire Transit Center (across from the Merry Time Tavern)), and the Columbian Cafe on 11th and Marine is a leisurely and very "local" experience, too.
Urban Cafe on Commercial (mid-block between 11th and 12th) is another good lunch or dinner visit.
The Maritime Museum at the foot of 17th has been remodeled since you visited, and worth a visit, also.
Even living here all these years, I still enjoy the Flavel House for its historic photos and local history.
Don't forget to check out how much more of the Peter Iredale's been nibbled away by the sand and sea, out at Fort Stevens.
You can see the rebuilt Ft. Clatsop and also hike the Fort-to-Sea trail if you're so inclined and the weather is agreeable.
Even the Column has new attractions. Buy a few balsa gliders and launch them if you dare.
On the Washington side, I like Long Beach itself for the Boardwalk. Or hike up to North Head and Cape Disappointment, visit Waikiki Beach, and all the attractions within the park. I'd skip Marsh's Free Museum in Long Beach, though, it's really gone downhill and isn't too much more than average compared to what it used to be.
In the Nahcotta area, there is Ledbetter Point and the hiking trails.
Whatever you choose to do, I think you'll like most of the changes, but do come see Astoria's quaint waterfront soon, as it's quickly disappearing into condominiums which of course will destroy the feel as well as the look.