We just did this two weeks ago, at San Francisco City Hall.
It was just us, the officiant, and one friend who was our witness and unofficial photographer.

4 people knew in advance besides the friend: my parents (they were all for it), his mom (also all for it), and his brother (against it).

We'll probably have some sort of casual party to serve as a reception/house-warming for our friends sometime next year (we're also in the process of buying a house).

I wouldn't do it any other way.

Best wishes!