Dead Money is much better than Honest Hearts. Your choice is ridiculous.
That's to opinion. I liked some things in Dead Money but I liked Honest Hearts better in spite of it's major shortcommings and the let down I felt at the small story Joshua Graham was attached to as I've awaited his character ever since Van Buren and his big bad "Hanged Man" role.
But yes you may play any of the DLCs in any order.
Other hand we've yet to see how they make sense of some Dead Money events and characters that are to show in Old World Blues and if it'll make sense if you play the DLCs out of released order.