Three days, even four really, probably means Santa Cruz
Island, likely the east end. There's a couple good websites detailing the anchorages
Smugglers is easy if a bit rolly. Give it a pass on a south swell. It gets you easy access to CINP, great kayaking and a short dink ride away from decent snorkeling. Yellowbanks is really popular, although also a bit rolly.
The front side is popular with the boats from SB. Pelican is pretty much standard, but can be crowded. Requires a Nature Conservancy permit
to go ashore. Great kayaking just west at Hole in the Wall. Watched a kid pull a giant halibut out right in the anchorage there after dinner one night.
Prisoner's Harbor is a fun
lunch spot on the way, is park land, and has some nice hiking and historic buildings (and restrooms). There's nice snorkeling under the cliffs on the west side, and the wreck of the "Santa Cruz" is visible from the surface. The wreck was the highlight of the summer for our son last year.
Plan on leaving early in the morning and motoring out for a while. Check the buoys before leaving. We like to return after lunch. The west wind
usually fills in and makes for a great trip back.
It's great fun. We'll be out a bunch this summer, although probably up more at Santa Rosa and San Miguel. Still, nothing beats Smuggler's for a quick weekend escape...