I know someone who had a bold coyote eyeballing a new foal last year. I don't know that it would have been successful but it unnerved him.
On the east coast, the coyotes have a large percentage of wolf blood in them, which is why they are bigger. There are also some wolves that were either pets (horrible idea) or came down from further north. Its breeding season for coyotes and they will be having pups soon so your coyote family may be growing over the next few months.
It depends on the mini if the coyotes go after it. I know some minis that will come after you with everything in the house including the kitchen sink. I would be less worried about coyotes chasing the mini and more about stray dogs. A coyote at least knows and has practice how to kill something a local dog is just playing around, which can mean more suffering for the animal.