I hate to bust your bubble, Sorta but we have threads with over a million views and hundreds of responses. You still have as way to go!
As far as the son goes, there are a million landlords who don't live near their buildings and can't watch the goings on and life goes on fine. Just a personal note, if it was me living there and you asked me why people were there or any other of my personal activities etc. I'd be extremely upset. It would 1000% creep me out if I knew someone was watching what I do. They seem like good people. Give them a chance to live quietly in the space they rented and unless the house is on fire or something is majorly out of order, I'd let them do their thing.