Have any of these adults completed Scoutmaster Fundamentals? If not, I would strongly suggest it. I make all the new leaders attend this training course. They will get a better feel for what the Scouts go through.
I would also stress that the Scouts are responsible for theis own stuff. Tell the parents to back off from picking up after their sons & then after everyone leaves, pick up all the left items. At the next meeting inform the Troop that some Scouts seem to have lost some things at the last meeting. Hold them up & have the Scouts claim them, BUT don't let them sit down until all the missing items have been claimed. Then, have them perform a Scouting song! Eventually, teh Scouts will get the idea!
Ed Mori
Scoutmaster
Troop 1