You have a few options… The easiest way is to simply place the apiary somewhere that mushrooms are already growing nearby. Another easy way is to construct a dark area near the apiary (such as a floating dirt platform) and plant the mushrooms there. A harder way is to produce mycelium using the moistener; with the mycelium you can plant the mushrooms in broad daylight. So lots of ways to deal with this issue, and no real need for a Forestry fix.
The large mushroom thing is interesting, though. If you can’t use those, it would be a nice touch to have them added as legitimate “flowers”.