This is an excellent stop for a family of cruisers, as the kid-friendly beach, swimming, and activities ashore will delight for days. And if you have guests who want to stay ashore, the simple but clean cabins at the National Park campground work quite well.
Like any of the northwestern anchorages on St. John, one must watch out for Johnson's Reef, which claims a few vessels every year from the unwary. It covers a broad offshore area to the northwest of Cinnamon Bay, and is well marked with yellow buoys. Other than that, Cinnamon Cay is your only hazard, and easy to spot.
It is preferred that you pick up one of the eight or so moorings to preserve the sea floor, but you can anchor in decent sand in the western end of Cinnamon Bay. The method for collecting the dues for the moorings seems to still be getting worked out, with pay stations ashore the latest incarnation. Check back here soon, or with the National Parks office in Cruz Bay for details before you arrive at St. John.
Cinnamon Bay has plenty to see and do ashore, without any serious village at all. The campground has a restaurant, small market, and a well-stocked watersports rental/lessons outfit. There are also hiking trails that leave from this area, including a fascinating tour of the old sugar mill/town ruins just across the road (definitely worth a hour or two detour).
If you're looking for a place to get married on a beach in solitude, check out the far eastern end of Cinnamon Bay. You will have drop-dead sunset views, almost no surf noise, and photogenic black cliffs and flowering plants as a backdrop. We've been there. It's fantastic!