The thing with toxic people is that they by definition create tension. No matter what you do, they will find a way to manufacture drama. You’re NOT the problem, the problem is the toxic person and at a stretch your lack of putting firm boundaries in place. You could meet with the new friends in the other city and not tell toxic person. And let them rage and blame and whatever when they find out.
You could ask to meet with the initial 3 friends one on one and maybe work on excluding the toxic person but there’s going to be plenty of tension. You have to decide if you can weather the tension or if you want to slowly have your friendships poisoned. You sadly can’t have both.