I follow your thread. Lots of good advice and support. I don't have experience with adult children so don't participate much.
I do know you can put a new password on your internet access every day if you want. It isn't to difficult and then you can give it to only the people you want to have it. Like a previous poster - I've also taken the router with me.
^^ The least of your problems. Good luck and so glad to hear you have an appointment scheduled.