I would think that just about any wood sealant would be ok as long as you alowed it enough time to dry good. I used white outdoor paint on the inside of one of my hoods, and regular wood stain on the outside of the hood, and have had no problems.
Why not use a piece of plexiglass and either use it alone or mount it to the underside of the wood so the water does not ruin the wood. Then, if you want, you can paint, stain or do whatever to the top surface.
