Thanks for the reply. Your suggestion is a good work around, but probably above my skill level at this time

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I am able to use the calendarfield extension with formauto by having first created a due_date as a text field and then changing it to calendarfield. This gives me an error when trying to save the field, but it does work on the front end. It includes the date in the email, but does not save it in the database. This may be sufficient for now.
Thanks again!