I was all worried about Episode 3 (which I put my foot down he will *not* watch before he is nine), but he didn't even make it halfway through Episode 2.
Moving on to the earlier movies, Episodes 4-6, I'm more worried about the sad roles that women have than about scariness. Quick, name a female character in 4-6 who is not Princess Leia. Hmm, yeah. I can't think of any either. Uncle Owen's wife, who is killed with her husband in the first half hour. Don't some of the Ewoks (the ones taking care of the baby Ewoks, unless I'm mistaken) wear sort of female-signifying clothing?
I think the part of Episode 4 that made the biggest impression on me as a 5 1/2-year-old was the garbage compactor, although Luke & Leia swinging across that abyss on a fishing line was a close second. I was older when I realized that it was really Luke swinging across, and he just sort of took Leia with him. At the time it didn't occur to me why there was only one woman character, and she was young and beautiful. I don't remember if I was disappointed in how she held her blaster as though she were scared of it, how she gritted her teeth and cringed while pulling the trigger. You could chalk it up to inexperience, but as I recall she was a pretty good shot, and wasn't Luke just as inexperienced? I don't remember him cringing.
Here's one that didn't occur to me until a few days ago: Han Solo calls Luke a kid all the time, but he makes no comments about Leia's youth. Of course, she is more worldly and sophisticated and seems older, but I don't think that's why. More likely it's because she is, in the immortal words of Alfie Doolittle, "old enough to be interesting to you gentlemen," and once a woman has reached that age, a man like Han Solo doesn't ask himself how old she is exactly.