I don't know if it will help or work but perhaps you can have plans to go out some of the time your guests are around. Like you might have to go to the library for a couple of the hours.

You are right, I don't think you can say don't come so perhaps you can go half way. Be there when they arrive, be polite and say hello and then go and do what you need to do for awhile, even if it means sitting in a park reading a book.