I use mushroom compost in my homemade potting mix. I can't imagine what a ton of it looks like! 48 square feet is just 6x8. What are you going to do with all the rest of it?
But yes, I think you would need to mix it with something to keep it from being heavy and compacting in your raised bed. For my potting mix, I use coconut coir and rice hulls. But the rice hulls while organic and sustainable and good enough for my purposes starting seeds, break down and disappear pretty quickly. What is traditionally used in potting soil is perlite and you can buy it pretty cheaply. Other alternatives would be coarse sand, pumice. Peanut or pecan hulls would not break down as fast as the rice hulls. Peat moss is traditionally used instead of the coconut coir.