Craig,
I don't know how many guest berths Treasure Island has; most people would just anchor out for the night. It is pretty protected from the wind and has a good bottom for anchoring. When you enter the cove, hug the north side of the entrance, there is a large shallow area on the south side of the entrance.
There is a pier missing, just south of the Bay Bridge and many boats will anchor in there to watch the show as the barge is set up right there. We anchored up for the night right there with Gene on Carolina Pacific a few years ago. It was a little rolly till the traffic died down, but after that it was pretty calm with an occasional ferry wake.
Navigating back to the Estuary at night is not difficult and there aren't any shallow areas to deal with. Just keep an eye on the buoys and your chart or chartplotter. I've done it many times without any problems. One piece of advice though, plan on remaining anchored for an hour or two after the show to let all the traffic clear out. There will be many boaters who have been drinking, ones with incorrect running lights and guys who are boating at night on the Bay for their first time.
