Books flying off shelves, faucets turning on — activity escalating over 3 weeks

We moved into our house in September and things started small. Knocking from inside the walls at night. The smell of cigarette smoke in rooms where no one has ever smoked. Then two weeks ago it escalated: kitchen cabinets all opened simultaneously while we were eating dinner. Last Thursday a hardcover flew off the bookshelf and hit the opposite wall with enough force to dent the drywall. We have two kids (7 and 10) and we are genuinely frightened. I've set up cameras throughout the house. On review I can see objects moving but no one near them. Our 7-year-old says she talks to "the man with the grey face" in her room at night. We're not religious people but we are running out of rational explanations.