Warning: cynic ahead.
Scott, I'm really glad you're thinking about this, most particularly as a parent. I don't really have much concern for your kids, I think you're a responsible dad. I think you're seriously in the minority though.
I agree completely with you about what this could do in terms of scaring kids - I think it will. I just don't think the majority of parents these days give much of a crap. I've seen kids at movies that have left me disturbed by a particular scene. That's just plain weird/wrong/stupid/illogical/inconsiderate of the parents to have their kids in there. But I think we're at a point where there's a certain numbness of brain in the bulk of people, so they don't think too much anyway. I'm sure there'll be a fair number of complaints, but really, you'd have to be pretty silly to not know what's coming, even if you're not a big SW geek who spends too much time on boards. It's all over the media and will be much more so in the coming 6 weeks. The story is well understood by even the most casual observer. If you've seen the OT you know Vader is evil and murderous; you know that the only Jedi left alive are Yoda and Obi-Wan, somehow the rest had to die. We didn't know what happened to Padme, other than that she is no longer around and her children were raised by other people, so that may be a shocker. Still, living under a rock necessary to not know the premise, if not the details.
That said, I agree with Chewie and Pete. What we've heard of this movie is what is necessary in this movie. I've long complained about the cutesy factor of ROTJ - I really do hate Ewoks. I really believe that was the start of the end of the glory of the franchise, something not present in either ANH or ESB. The Ewoks spawned Jar-Jar and the sound of music cutesy, lovey scenes in AOTC. Blech to all of that. Not necessary to the story, not required to draw in fans. Just dumb plot devices that, IMNSHO, failed. ANH and ESB are the most widely accepted as the best two movies of the franchise (post-pubescent crowd). Leia/Han's romance occurred in what, a grand total of maybe 12 minutes over three movies? No furry, funny, cute side characters in either of those movies. No, this movie has to be dark, very dark to take it back to where the plot starts for ANH.