I've stayed at the Sheraton on the Wharf, I'm not sure if they sleep 6 though - recommend.
A friend has stayed at Pier 2620 again I don't know if it will sleep 6 - recommend.
Another friend has stayed at Columbus Motor Inn which does sleep 6, she recommends it for larger families on a budget but advises it isn't flashy, and a little run down. I think they have a few family rooms but unsure what the bed configuration is like - maybe a pull out sofa in the lounge.