I think that having an outlet for your excess energy is a good thing for anyone, but especially for people with ADHD. so yes, I think doing theatre would be good for you. I also think that people with ADHD tend to be more spontaneous, more wiling to take risks and go off on a whim, etc, which can really help them be imaginative and creative. If theatre is a source of hyper focus for you, then that is great too, because when ADHDers hyper focus, we put 100% into whatever we are doing.