The WeatherStation is a little "pricey" ($235-355 per night), though it looks very nice. If the Fairfield Inn is indeed far from the action & not walking distance from the ferry dock, I would like to know if something more reasonable is 'downtown' -- and walking distance from the dock for a couple seniors.
The Fairfield is definitely not "walking distance from the dock for a couple seniors". KW is not known for its "reasonably priced" accommodations - it typically leads the state in nightly occupancy percentage and rates.
If you are only going to be there a couple of days, you definitely want to stay in the Old Town area as suggested above. The Westin, Ocean Key, Pier House, Hyatt (Resort & Spa) and Galleon (actually TS, but they rent a lot of rooms/units by the night) are the popular hotels at the lower end of Duval - while all of these are short walk from the Fast Cat dock and are an ideal spot to explore Old Town KW, the nightly price will reflect that. Note that I've listed these hotels in order from farthest (Westin) to closest (Galleon) to the Fast Cat dock.
Instead of a hotel, a lot of KW travelers go the B&B route (nightly prices can be better and they tend to have a little more of the "flavor" of KW) - you can check price & location of hotels and B&B's here -
http://www.tripadvisor.com/Hotels-g3...ACCOM_OVERVIEW
Part of the attraction to KW is that it can be as wild or as mild as each person prefers it. Wild - bars close at 4 am (if you prefer to drink naked, the Garden of Eden would be the place for you). Mild - walking thru the side streets of Old Town observing the beautiful old homes. Throw in the variety of historic sights (Mel Fisher's Museum, Hemingway's House, Audubon House, etc) and wonderful restaurants (Sarabeths, Marquesa, B O's Fish Wagon, Blue Heaven, etc) and 2 days will be gone in a blink of an eye.