I forget whether it was this film or the re-release of The Sound Of Music, which was my first movie experience in a theater. And that theater was Radio City Music Hall. On a big screen, this film was quite impressive.
In my linked post, I erred and thought this film was called You're A Good Man, Charlie Brown, but the correct title is above. I recall the river rafting sequence, and, somehow, it's as if 40 years pass by in a whirr. Too, I recall Julie Andrews' mien on the big screen, but even more so than the first Christmas tv special with the Peanuts gang, this film is the definitive Charlie Brown, to me.
Here is a link to the film.
Here is the opening sequence: