Council Rock School District officials have canceled lunch cruises for sixth graders from seven elementary schools after receiving information about a plot to poison children’s lunches. The plot was outlined in an anonymous handwritten letter sent to the Chicago company that operates the Spirit of Philadelphia cruises on the Delaware River.  It said two parents at Goodnoe Elementary School planned to sicken the children, including their own, and then sue the cruise line.  Newtown Township Police are investigating, but they say they don’t have much to go on because the letter is vague and the postmark is obscured and unreadable.