Just based on experience, if other parents are talking about it, it's already disruptive. They will watch to see if you act decisively and that will inform how they behave in the future. It's in everyone's best interest to just tell the problem parents you know they don't want to be there so you will make it easy and let them go. No hard feelings, best of luck, etc.That is basically what I am doing. No need to do anything else unless something becomes really disruptive.