Possible Mimic

I live with my husband and 2 teens in a cul-de-sac that borders woods. We all love spending time in our yard and enjoying nature. On two occasions now my kids have told me about some eerie experiences they've had. My kids recently got a trampoline and love to be on it even at night. Recently, they heard whistling and conversations from the woods around 10pm. Now I can assure you nobody goes down there (wooded embankment too) except in hunting season. This really freaked them out and they came in and told me right away. I should mention we have a cat that escapes sometimes and we end up in the yard looking and calling her name. Another time, my son was out around dusk looking for the cat near the border of the woods. He was by himself and his sister was inside. He said he heard his sister calling his name from the woods twice and then giggling. This was very unsettling to say the least. I want to cameras for the yard. Not sure what's going on. Any ideas?