Ditto on requesting a specific loop, make your particular wishes for the site known. I had my heart set on getting into the 1400 loop this past trip, mainly because I wanted to be near the Meadows Trading Post and the campfire/movie area. I think if I had let them know about the wish to be near the campfire and Meadows, they would have found something closer.
Instead, all they knew was that I had a 29 foot trailer with a longer truck and planned to use a tent. We got a great site for that, very easy to back into and get out of, plus lots of distance front to back which allowed us to have the tent behind the trailer and still get the truck in front of the trailer. But it was in the 400 loop and far from the Meadows area. Close to the Marina and Pioneer Hall, but I never did make it to the campfire and movie (second trip to the Fort), and my youngest kids are 8 and 9. Not sure if they'll want to go to the campfire when they are older.