Cyn, I know it's a bit rough, but hang in there.
My daughter, and grandkids come stay with me frequently. I actually enjoy it when they do. The only reason I have mixed feelings about them going back home, glad, but sad too, is due to the ages of my grandchildren. They're very young, and so full of energy, but not yet old enough to somewhat independent, and self reliant, so they wear me out.
Having my friend, and her grandson stay with me was not the problem. There's more to the story regarding when my friend stayed. The issue was how the rest of her family came pouring in on me uninvited, what they expected from me, and how they treated me.
My suggestion is to stock up on Solo type plastic cups, and plates, plastic silverware, and fix large easy meals like spaghetti, stew, chicken and rice, chili, beans and rice, neck bones and rice etc. Set it out, so they can help themselves, and you don't have to serve them. Clean up is so much easier that way too. Take a marker, and put each person's initial, or name on a clean plastic cup each morning, and that way you don't go through a ton of cups. Don't make anything harder on yourself than you have to, especially if there is an easier solution.