We just returned from a wonderful, scenic, relaxing cruise from Vancouver, WA to Clarkston, WA on the American Empress paddle wheeler up the Columbia and Snake Rivers.
It was extremely enjoyable in every way. The age group of the passengers ranged from the 40's to the 70's. Unlike ocean cruises, getting off the boat at various stops along the way was extremely easy for even the handicapped (elevators are the same as ocean cruise ships). They provide hop on/hop off busses at every stop along the way, making it pleasant and easy to see every sight. Everything is included with few add-ons. Wine and beer are included with dinner, but normal bar drinks are extra.
I highly recommend taking the jet boat excursion in Clarkston. It's a trip for everyone to enjoy the spectacular Hell's Canyon in Idaho which is deeper than the Grand Canyon and a beautiful sight and experience. We saw more wildlife than we did in Alaska, including mountain goats and bighorn sheep. The towns along the way are quaint and historical.