Hi M.: My first thought after reading your request was "Why is she so quick to blame her son for the mess." It makes me wonder,if you were an only child. I come from a large family,and to this day, we are (loyal) to one another.If anyone accused one of my siblings of misdoings,we would all rallie together and defend their honor. I think its vital, that your son feels you and his father are there to back him. At his age, its a little difficult to defend himself..You admitted that your son doesn't normally make a mess, but when he has another child visiting,its demolished.Hmmmm lets see...you think that kid visiting just sat there twiddling his thumbs, while your son went (Beserk)?? I don't think so.... When my sons friends would come over, they pulled out EVERYTHING!! They wanted to check out all the toys they had. I knew who had made the mess, without even asking...My sons had all those tiny leggo toys they out grew and put way up in a box to give away. What? one visiter,and NOW my sons are interested in the leggos again? Don't think so! My oldest got real upset,and said....does that kid have to come over? He ripped everything out of my closet!!Now I have to clean it all up!!Don't be so quick to judge your son. The other kid is company,and while I know you wouldn't scold him with his parents right there, you can tell him, that he is welcome to play with your sons toys...as long as he puts back each toy he brings out.Then check on them periodicaly and get him to pick up a little at a time,because HE KNOWS your not going to ASK HIM to clean up while mommy and daddy are standing there waiting to go home! best of luck