Hi @matt_collingwood
Setting your project members to ‘Commenters’ should lock the ability for them to make any changes to the project and its tasks. However, any assignee will be able to make certain changes to the task they are assigned to, including the due date.
You can refer to the table in the Asana Guide here (refer to last column ‘Commenter with task assigned’):
To keep better track of changes to due dates, you could use the new Gantt view which includes a Baseline feature which will visually show you changes to any dates.