RenWeb has a single check box that connects these three components.
While entering an assignment in the grade book, if the "Publish to Lesson Plan" field is checked, then the assignment will appear on the teacher's lesson plan. If a different due date is given from when it was assigned, the item will appear on both dates in the lesson plan book.
As an added bonus, the assignment date and the due date also appear on the Parent Web side. Students and parents can click on the Homework Assignments heading to see each graded item.