You should be able to grow shrooms with your current light setup with no issues at all. I was growing toadstools, zoas, shrooms, gsp under a 4 bulb t8 setup in my 75. I just bought a deep blue solarmax t5 fixture. For the money its really really nice, programmable doesnt get too hot and imo well worth it.
The clowns will decide on what is going to host it. I had a clown be hosted by a filter tube before. I also had one be hosted by a a toadstool. They typically seem to go for corals that are similar to the tentacles of an anemone. Some corals do not take well to hosting clowns.