Seattle on a budget?

Help my dream come true: to visit Seattle!
We would need lodging 3 nights, 8/27–8/30. I found a really good deal on airfare, but if we can’t find accomodations we’re beat. Lodging is for 1 adult and 1 child. Is it possible to find a room in a safe section, not too far from attractions for less than $100/night, or am I dreaming?