A few thoughts
I wouldn't recommend keeping a Sunfish in the water, though some may disagree. There's no good way to keep it covered on the water, so you'd find yourself with mucky water in the footwell, grunge on the bottom, and probably bird poop on the deck. In addition, I don't think it's very practical to rig a floating Sunfish ... that's a lot easier while it's on a trailer or tied up at the beach or in the shallows.
That said, find one with a trailer or a dolly and you can probably still keep it at the club. You'll be able to cover it, and pop in the mast and sail on the hard. Launching with a trailer or dolly is very easy.