While songs from the general "cowboy" tradition are fine, if grade schools are even vaguely similar to a hundred years ago when I was there the music books used in the schools likely will have at least a few songs with suitable themes that the kids will already know.

While it's obviously too late for a program "in a couple of days" my suggestion would have been to call the nearest gradeschool and see if you can contact the "music teacher" or at least learn what book(s) they're using at around 1st or 2d grade (in the US).

Obviously what's taught may have changed since I was 7 years old, but since in Kansas teaching has gone backward another hundred years but other schools have claimed to have "gone forward," you might get lucky and find what you want if you happen to live where it's "tweeny."

That's about the right age for "Cub Scouts" and a "Pack Leader" or "Den Mother(?)" might know what songs the kids would be likely to know, but with this approach you'd need to give equal time to the girl groups(?) - political correctness and all that.

John