Is there a basic flight pattern that a newbie could fly at the Nats?
There are two introductory patterns for new pilots. the first one is "Basic Flight" and the next is the "Beginner" . You might search around on the forums here for descriptions of each. Basic Flight is pretty basic, just get it started and off the ground, some climbing and diving, and loop or two, stuff like that. The Beginner class pattern, if my memory serves me correctly, is 1) Take Off and Level Flight, 2) Wing Over ( Not Reverse ) 3) 3 Inside loops, 4) 3 Outside Loops, 5) 2 Inside Square Loops, 6) 2 Horizontal Figure 8s 7) 2 Over Head Figure 8s,

Landing. This is all to be done in the same 8 minute time limit as the full pattern, but some clubs shorten the time limit to 6 minutes to move things along if there are a lot of beginners. That will keep him challenged for a while. Look into joining PAMPA, and there is much to read, learn and download on their website.
You have the right idea on how your grandson should progress. Let him advance at his own pace. Getting out to fly with others and watching them do the pattern is good motivation, especially if there are other kids flying. They tend to relate to each other better and can be a big help to each other.
Welcome to the party pal!! Have fun!
Type at you later,
Dan McEntee