The hotel you mentioned, The "Seattle Marriott - Watefront" should be okay as well, as it's along the water, but probably more expensive than the Quality Inn. Unfortunately, Mapquest isn't recognizing the address of the cruise terminal when I go to put it in, so I can't give you an estimate as to how far it would be from the Marriott to the cruise terminal.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)