I would just like to point out the obvious that if you're using dates, it's not really agile.
Kanban as far as I'm aware is a pull when ready system, not a 'I must to get it finished by some prescribed date system'. That said, I don't mean to be unhelpful and there are times when dates are useful. As long as the system isn't designed in such a way that the prominence of dates sends the wrong messages or lessons to others that should be OK.
I'm sure there are other fields that people would like displayed on the cards too, so perhaps a better way might be to make any of the items within the task an optional item to display next to the task? (I think you mean on the card?)