Possums aren't aggressive. They only bear their teeth to scare us off. It reminds me of a slimy salesmans grin and laugh when I see it. They might hurt one of your dogs only if they are cornered by them.
I used to have a pair that would have a dinner date on my hanging bird feeder after dark. You will know if they get into the sunflower seeds as they regurgitate the hulls in nasty wads. And I agree they serve a purpose in nature.
The coyotes on the other hand will kill and eat small dogs, cats, whatever. I agree in hoping they don't move into your area. I have an acre under fence for my pets to remain safe in and some nights the 'yotes come right up to it. They are fearless.
