Well, leather masks wont be a burn concern unless you're using flammable paints on them. In fact, they'll provide you with an additional level of safety for the face if something does go wrong!
Unfortunately, they also do increase the difficulty level of spinning. The ones we're using actually have ears and extensions off the face (Bast and Anubis), which make certain things harder. Just practice with them on, be more spatially aware since you'll lose some peripheral vision, and try to avoid flammable paints. Past that, its totally fine, and the masks are definetly a better thing to expose to flame than your own face!