Unfortunately, there isn’t a “change reservation” option. You have to cancel the park pass reservations you have and then make new ones, which is very risky this week. If you decide to try it, I would try one person at a time. If you aren’t able to pick up an Epcot reservation pretty quickly, I would try to pick the DHS pass back up and then try again later. That said, as many other people are also looking for these park pass reservations this week, your DHS pass could be gone by the time you try to pick it back up. If I were in your position, I’d find something else to do that morning (if you’re really not interested in going back to DHS), and hop to Epcot at 2.