I got up and did this power walk this morning. And I'm glad I did. The gentleman cast member who takes you on your DCA journey is Dave from Anaheim, and he is very nice and talkative. One note ... they say to get to the Grand DCA entrance at 6:55am to sign a waiver before your 7am start. Do not be late! We left about 30 seconds after 7:00am. The CM who stayed back at the gate told us 4 folks showed up just a minute or two late, and unfortunately missed it.
Anyway, it was Dave, me, and one other guest, and we set off on a counter-clockwise trip around DCA, going around Paradise Pier, through Pacific Wharf, into Cars Land. Then past Luigi's into Bugs Land and past Tower of Terror and the Monster's Inc ride. Then off to Soarin' are past our starting point. Then we went through the Redwood Creek Challenge Trail (including over the rickety wooden bridge), and back past the Painted Ladies towards Ariel's ride, and then left to the Carthay Circle restaurant and Soarin' again. Here we ended back at the hotel. Dave told us we went 1.8 miles, and that once Grizzly River Run opens, the walk will make one loop around the Grizzly Trail to make it 2 miles.
We were back at 7:27am or so, and the extra loop would have taken an extra few minutes had it been open.
I highly recommend getting up for this. They tell you no cameras, but Dave let the other person in our party take a Cars Land picture, since the picture wasn't of anything "backstage". So you likely can bring your camera.
We did see a dozen or more cars and trucks on the roads, especially in Cars Land. And several of the doors to behind the magic were open, allowing a glimpse or two behind the facades that aren't normally there.
You do not need a park ticket, so you can do this on your departure day if you don't have any days left. Call ahead and reserve your spot, although I think you'd be fine if you just showed up at 6:55am.
Thanks for reading. I hope this helps.