That is an excellent idea!  Yoga is perfect for runners because it helps improve flexibility, which can be a problem for runners who don't spend extra time on flexibility.  This will help prevent injury, which is a good thing, but yoga has so many great benefits on it's own!  I practice Kundalini yoga and every now and then throw in a hot yoga session, and I find it extremely refreshing and a great way to improve the body for running.  Definitely do it.  It will definitely be a good decision!