Sorry if this response is late. If you have not yet finished the main questline, I would highly suggest doing the dlc before completeing the game.
TOW plays out much like Fallout NV did. Once the main quest is completed, that's the end, there's no playing beyond that.
Another option would be if your nearing the end but have not yet hit the point of no return, do a manual save, complete the game, then reload the save.