[brianogilvie]

By "delay," do you mean change the start date or the due date? If you frequently find yourself changing due dates, you should rethink whether to use them at all. A due date should be used only when you have a commitment to finish an action or project by that date. If there are no consequences to missing the due date, the action or project wasn't really due by that date.

But to get down from my soapbox and answer the question: there are two ways to do this:

1. Select all the tasks and use the Action Inspector to enter the new start or due date.

2. Change the project's start or due date. Note that if an action has a due date that is sooner than the project due date, this won't work.