In another thread came up the discussion is/was SW for kids/adults:
http://originaltrilogy.com/forum/topic.cfm/The-original-ending-of-Ponda-Baba/post/532219/#TopicPost532219
and zombie84 mentioned how the PG ratings were changed, which is one sign of them attempting to appeal to both audiences.
Here's another example of appealing to both:
http://www.ew.com/ew/gallery/0,,20399642_20511617,00.html#20990635
'Star Wars': Comic-Con '76 pics!
In the photos is a one page which starts with the following quote:
[Star Wars letterhead]
"I have wrought my simple plan
If I give one hour of joy
To the boy who's half a man,
Or the man who's half a boy."
--Arthur Conan Doyle's preface to "The Lost World"
and this might be the oldest reference photo of SW out in the wild: (but looks like a still not part of the film...)