Only snorkeled, very cool, totally worth it. We have done it twice with Tulu. He can get lights, but we brought water proof ones just in case. I think the dive outfits provide everything for you. Do it!
We do night dives outside the reef when conditions are calm and at Hol Chan. We provide lights. It's a good idea to do a day dive at the same site that the night dive will be, as you'll be amazed how different the two dives will be.