when u say "automatically start communicating with your router and potentially start broadcasting your multicast traffic" this implies u don't want them to get multi cast ?
in this case simply do not enable pim towards them. even if the try to join any groups, they will not get any feeds.
but if ur peers are meant to get multi cast but simply not feed it back their own peers, use ttl on ur interface to limit multicast packets life in tyerms of hops.
HTH
Sam