{quote]I'm going to take the boys out for the day after they get home from haircuts. I won't invite H but if he tries to come?? Just say I don't think that's a good idea? I suck at this.[/quote]
You know this. Calm, cool, and collected boundary setting.
"No thank you. Have a great afternoon."
or
"I don't think that's a good idea."
or
"We talked about this already. You made a choice and things will change as a result of that choice. We'll see you soon. Bye."