This page seems to imply that there is no shuttle service in Bryce in December. So I assume the only way to get to trailheads for a group of people is by car. However, I was unable to find any information about parking on the official website, and I don't see any parking lots in Google Maps. Where can one park in Bryce Canyon (say, in the walking distance of the Sunset Point)?
Sunset Point (and all the other named points in Bryce) all have parking lots of various sizes, as well as a well paved Rim Trail that connects all of them. In particular, Sunset Point's parking lot probably fits 60-70 cars.