There are four marinas in the downtown Grand Haven area.....The City Municipal (that week it goes by lottery), North Shore (wrong side of the river in my opinion), the Yacht club, and The Warf. All will be full that weekend. You might try Barrets, Grand Isle, or....damn.....what's the name of the place on the left side as you come into Spring Lake????? Shoot!!!!!!!
If you just can't find anything there, Muskegon is only 12 miles north, and Great Lakes is a nice place to stay. Lot's of OSO members run out of that marina.