I never caught enough fish to use them but I always planned on bleach. As far as using plywood, I believe it will be as bad or worse. The wood will allow stuff to get in between the fibers. I think that's why wooden cutting boards are discouraged.
How about one of those cleaning tables you can buy at academy? It's small enough to keep in the bed of your truck, and the surface should be safer.
http://www.academy.com/shop/pdp/cold...tion/pid-14347
Pointe aux chene marina has a cleaning station that is screened in. That would work at calcasieu point to keep the birds away.