It would be a stretch, but anything's possible. The second HDDR show begins at 7:15 so you will be on your way by then. Are you doing Dtransportation or driving?
For Dtransportation you have a few routes to choose in case one has a very long waiting line:
To Magic Kingdom: Walk to the Marina and then board the Magic Kingdom boat from the dock.
Alternate route #1: Go to Settlement Depot, board the Contemporary boat, get off at the Contemporary, and walk to the Magic Kingdom or take the Magic Kingdom boat.
Alternate route #2: Board the Crockett or Boone bus, get off at the Transportation & Ticket Center (TTC), and transfer to the Magic Kingdom monorail or take the Magic Kingdom boat
So it is more than possible if you keep everyone moving!