I was about the age of your oldest kid when I first saw them, early 90's on my uncle's poor VHS tapes. Besides getting scared of the first time Darth Vader arrived on the Tantive IV (and that's the only clear memory I have of my first time watching Star Wars), I don't think there's anything unsuitable for a child.
Besides, Ewoks at the end of Jedi is much easier to swallow and not get too bothered by if you watch the movie as a kid.