You know what's cute about this ad? It looks like some ad guys mocked the whole thing up with photos of kids and real Charles Schulz drawings, and then one of the ad guys' teenage sons who draws pretty good, I guess, traced over the whole thing with marker. "No pencil sketching first, Mom!"
Seriously though, it's a cute and fun ad and a sign of cuter and funner ads to come. I personally like the word/thought bubble you can fill in yourself (instead of "Curse you, Red Baron!" I wouldn't be surprised to see "Curse you, Whitey!" written instead), and the typical mundane airplane model stand shaped like the front of Snoopy's doggy door.
From Amazing Spider-Man #89, November 1970.