Two nights ago, my children had their three cousins over for a sleepover (two sisters aged 15 & 16 and their 11 year old brother). We've had them over many times before without incident. However this time, when I woke in the morning, I found a bunch of mysterious things had happened in my kitchen and living room which included items being switched and moved around, a pile of pistachio shells left on my brand new couch, dog food inside the cheesecake that was on the table (which my unknowing daughter had eaten some of that morning), writings and scribblings on my kitchen counter in permanent marker, etc.
Long story short, for various reasons (I won't get in to them), my husband and I both believe it was our 11 year old nephew who did it. He would have had the opportunity as the girls were sleeping downstairs and my son often falls asleep before he does. However, when questioned, he (as well as all the other kids, including my own) swore up and down that they had nothing to do with it. Even after my son (who is 6) started crying, worried that our house is haunted and stating that he wants to move, he did not come forward. I know my children very well and would bet my life that they had nothing to do with it or know nothing about it. I also do not believe that the older girls would have done it either.
In the end, there was no permanent damage done (thankfully, I was able to remove the permanent marker from my counter using magic eraser), however, I'm quite alarmed by it as it's pretty sneaky and the bold faced lying without any kind of remorse bothers me (there was plenty of opportunity to come forward with a promise of no repercussions).
Is it worth mentioning to their parents? My gut says to just let it go as I don't have any concrete proof. Should I just chalk it up to a practical joke gone wrong and take care next time I invite them over? How would you handle this?