Welcome to the Forum Madcorle:
First, I would not trust a wood sandwich beam, unless it had a 3/8" thick steel heart in it. A glue laminated beam could be made for the situation using a 2 to 3 inch camber in it, 8"wide and at least 12" thick; now you are talking about a lot of weight again.
I think you should go for the steel beam and cover it since it is in your realm of experience. I would consider the least amount added to the beam possible; for instance, 1 X 1 nail strips along each lower edge and cover with 1/4" plywood. The ends should rest on as many studs as you can get under it. Please post back, maybe with pictures, and let us know how it worked out.