If you book on DL you would have to book in the top coach fare bucket to have the ability to upgrade with CO miles. If you want to upgrade using DL miles there are a couple more - slightly cheaper - fare buckets you can use but not all of them.

If you book on CO you can upgrade from any fare using CO miles but it will cost you cash + miles in advance. Or you can risk it and go for the REVUP approach which is cash only but only available within 24 hours of departure for elites or within 2 hours of departure for non-elites.

Also, look at the fares from PHL if that is at all reasonable for you as a departure city. Those fares are often significantly less. And check LGA, too.