M.C.
We had a friend whose house was the hangout house. They did a flag system... They had a big green ribbon a red one. If the kids could play, Green ribbon was on the window. If they didn't want anyone knocking on their door, red ribbon. Maybe you could do something similar? That way, you aren't having to constantly reply to texts or phone calls, and you don't even have to contact the parents of all the kids. Just start hanging the ribbon, and next time they come over explain the system to them. Then just become really strict about enforcing it.
It also works as a chore incentive/disciplinary tool. Kid can't put up the green ribbon and play until after chores/homework is done... Bad behavior means the red ribbon goes up and they can't go out with their friends.